MTS4CC
Elementary Stream Compliance Checker
Tutori a l s
001-1415-00
This document applies to software version 1.0 and
above.
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Table of Contents
Getting Started 1............................................
Basic Functions 2..................................................
How to Begin a Tutorial 2...........................................
Tutorial 1: H.263 Standards Compliance and Motion Vectors 3.....
Procedure 3......................................................
Conclusion 8.....................................................
T utorial 2: MPEG-4 Compliance 9.............................
Procedure 9......................................................
Conclusions 15.....................................................
Tutorial 3: MP4 Compliance Basics 17...........................
Procedure 17......................................................
Conclusion 22.....................................................
Tutorial 4: MP4 Optimization 23...............................
Procedure 23......................................................
Conclusion 28.....................................................
Tutorial 5: MPEG-4 and H.264/AVC Buffer Analysis 29............
Procedure 30......................................................
Conclusion 42.....................................................
T utorial 6: MPEG-2 Compliance 43.............................
Procedure 44......................................................
Conclusion 52.....................................................
Tutorial 7: Fidelity Analysis 53.................................
Procedure 53......................................................
Conclusion 62.....................................................
MTS4CC Elementary Stream Compliance Checker Tutorials
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Table of Contents
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MTS4CC Elementary Stream Compliance Checker Tutorials
Getting Started
This set of seven tutorials helps you learn more about operating the Tektronix
MTS4CC Elementary Stream Compliance Checker. Perform tutorials 1--7 in the
order they are presented, regardless of the video standard of interest. Tutorial 6
relates only to MPEG-2 and interlaced video.
The tutorials will help you answer the following questions:
H How do you know that your video compression complies with the standards?
H If your codec doesn’t work well with other vendors’ codecs, where is the
problem — is it with your codec or theirs?
H Codec optimization:
H Are you making the best use of available bandwidth?
H Which frames and movement types use the most bits and why?
H What changes to your codec software give the best reductions in bits
used for the least reduction in visual quality?
H What types of video content does your codec work poorly with and why?
Table 1 includes a description for each tutorial.
Table 1: Tutorial descriptions
Tutorial Name Standard Areas Covered
1 H.263 Compliance and Motion
Vectors
2 MPEG-4 Compliance MPEG-4 Simple Profile Common errors; searching for areas of
3 MP4 Compliance Basics MP4/ Simple Profile/ L1(2) Extract and examine container files; level
4 MP4 Optimization MP4/ Simple Profile/ L1(2) Using MB type overlays and searching for
5 MPEG-4 and H.264/AVC Buffer
Analysis
6 MPEG-2 Compliance MPEG-2 Main Profile / Main Level Syntax errors; MPEG structure analysis;
7 Fidelity Analysis MPEG-4, MPEG-2, and H.264 Fidelity analysis; visual difference.
H.263 Baseline Errors and error log; motion vectors.
codec optimization.
conformance error.
areas of optimization.
MPEG-4 ASP and H.264/AVC Buffer analysis in MPEG-4 and
H.264/AVC; fixing problems.
interlace.
MTS4CC Elementary Stream Compliance Checker Tutorials
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Getting Started
Basic Functions
To complete the tutorial procedures, you must be familiar with the basic
functions shown in Table 2. To perform the desired function, click on the
associated icon or type the appropriate keyboard shortcut.
Table 2: Basic functions
Function Forward Backward
Icon Keyboard shortcut Icon Keyboard shortcut
Play video Ctrl + P Ctrl+Shift+P
Stop video Ctrl + S Ctrl + S
Pause/step one frame Ctrl + A Ctrl+Shift+A
Fast forward/backward Ctrl + F Ctrl+Shift+F
Pauseonframe
Skip to next frame type/number/time Ctrl + K Ctrl+Shift+K
How to Begin a Tutorial
1. After starting MTS4CC, click anywhere to remove the splash screen. If you
do nothing, the spash screen will disappear after 4 seconds.
2. Load the desired tutorial stream. Note that the demo version of the MTS4CC
will only play the provided example video files.
2
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 1: H.263 Compliance and Motion Vectors
This tutorial covers the standards and compliance issues in H.263, and also
demonstrates the proper functioning of the motion vectors.
Procedure
1. To load the H.263 tutorial, click File > Example files > H.263 stream >
Rally (250K). The window title changes to MTS4CC-H.263 Example -Rally (250k), and a warning message appears, as shown in Figure 1.
Figure 1: Initial warning message
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 1: H.263 Compliance and Motion Vectors
2. View the warning message elements:
H Warnin g -- Indicates that the PSUPP field is being sent and ignored.
H Summary -- Gives summary information about the stream.
H Skip this Warning only in the future -- elects to skip this particular
warning in the future (recommended).
H Skip ALL Warning alerts in the future -- elects to skip this alert and
all other alerts in the future.
3. Select Skip this Warning only in the future, and then click Continue.
4. Click the
The error message shown in Figure 2 appears.
5. View the error information provided, which indicates a more serious error
that occurs at bitstream byte address 0x0c9cfa, bit 3, after frame 326.
toolbar icon or type CTRL + P to resume playing the video.
Figure 2: Initial error message
4
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 1: H.263 Compliance and Motion Vectors
6. Click Continue. An error message appears, as shown in Figure 3.
7. Note that it was an MBCPC error that resulted in the Out of Sync alert
message shown in Figure 3. This often occurs when one syntax error triggers
a series of alerts.
Figure 3: Out of sync error message
8. Select the Skip ALL Error alerts in the future check box, and then click
Continue.
9. To open the Alert Log, click the Alert Log icon
appears, as shown in Figure 4.
10. Note the active filter button in the toolbar. B ecause Skip ALL error alerts
in the future was selected, the alert log view is filtered and the filter button
is active. The status bar indicates that 23 of 24 alerts are hidden.
11. Click the Filter icon to deactivate the filter and view all alerts, as shown in
Figure 5.
. The Alert log window
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 1: H.263 Compliance and Motion Vectors
Figure 4: Alert Log window, filtered
Figure 5: Alert Log and Alert Details
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 1: H.263 Compliance and Motion Vectors
12. Double-click an alert to view the alert details, as shown in Figure 5, and then
click Close. View the columns that appear in the alert log, which are shown
in Figure 6, and note the column descriptions that follow.
H Level -- the severity level for the alert. Levels include Info, Warning,
Error,andFatal.
H ID -- MTS4CC unique alert ID number.
H Class -- Syntax area where the alert occurs.
H Title -- Alert title.
H Decode and Display -- Frame numbers where the alert is decoded and
displayed (can vary).
H Address -- The address of the alert in the bitstream.
H Details -- Alert details.
Figure 6: Alert Log, unfiltered
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 1: H.263 Compliance and Motion Vectors
13. Close the Alert log and return to the main page of the application.
14. Click the
visible. An image of the video is shown in Figure 7.
15. Note the following about the image:
H The white dots are at the center of each MacroBlock.
H The white lines indicate motion vectors. The arrows for each MV point
to the position in the previous frame that contains the data for the current
MacroBlock.
16. Click the color transfer icon
17. To play the video again, click the icon or type CTRL + A. Note that the
motion vectors are clear and accurate.
icon to play the video again with the Motion Vectors (MVs)
to change the overlay from white to black.
Conclusion
8
Figure 7: Video image
This tutorial demonstrated where there is a standards-compliance issue in the
H.263 bitstream, but also showed that other aspects of the H.263 bitstream, such
as the motion vectors, are implemented properly.
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 2: MPEG-4 Compliance
This tutorial covers the following:
H Basic functions
H Alerts for syntax errors
H Video summary tooltip
H MacroBlock overlay MB types
H Optimization
H Frequency of intra-coding
Procedure
1. To load the H.263 tutorial, click File > Example files > MPEG-4 Elemen-
tary Streams > Space. An error message appears, as shown in Figure 8.
2. View the error details:
H The error occurs at bitstream byte address 0x11, bit 3, before VOP 1.
H The error is present in the header, and MTS4CC does an initial check of
the file header when it loads the file.
H The error indicates that method 1 quantization is in use, which is not
allowed because the stream is Simple Profile.
3. Click Continue. MTS4CC loads the stream, and the window title changes to
MTS4CC-MPEG4 Example-Space.
4. Click the
error message shown in Figure 8 appears again.
5. Click Continue. A warning message appears, as shown in Figure 9.
icon or type CTRL + P to resume playing the stream. The
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 2: MPEG--4 Compliance
Figure 8: Initial error message
10
Figure 9: Initial warning message
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 2: MPEG--4 Compliance
6. Click Goto, andthenclickHex, as shown in Figure 9. The Hex view
appears with the error location highlighted, as shown in Figure 10.
7. Close the Hex view, and again view the error shown in Figure 9. The error
occurs because modulo_time_base was set to 1 after a whole second elapsed
since the modulo_time_base was last 1 (at which time vop_time_increment
should be reset, although not necessarily to zero).
8. Click the
alert shown in Figure 9 appears again.
9. In the alert dialog box, select Skip this Warning only in the future,and
then click Continue.
10. Complete the video and observe whether it works properly.
icon or type CTRL + P to resume playing the stream. The
Figure 10: Hex view with error location
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Tutorial 2: MPEG--4 Compliance
11. From the Overlay menu, click Video summary tooltip to enable the Video
Summary tooltip.
12. View the Final Video Summary T ooltip, shown in Figure 11, and note
these field descriptions.
H Picture size: 352 pixels high x 288 pixels wide (CIF).
H File size: 976 kBytes.
H Total frames: 175.
H Total play time of the sequence: 13.920 seconds.
H Total bits: 7,998,576.
H Bandwidth required to transmit this: 574 kbits/second.
H Frame play rate: 12.50 frames per second (Hz).
H Clip is MPEG-4 Simple Profile with Resync markers & Method 1
quantification.
13. Observe how the sequence looks, and then close the Final Video Summary
window.
12
Figure 11: Final video summary tooltip
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 2: MPEG--4 Compliance
14. To see if the codec makes the best use of the MPEG-4 standard, open the
Overlay menu, and then click MB Types (you can also type CTRL+ Y).
The MB types color key appears.
15. Move forward 3 frames. The MB types are color-coded as shown in
Figure 12.
Figure 12: MB Types color key
16. Move forward to frame 34. As shown in Figure 13, note that there are
several green (intra) coded MacroBlocks in the static black background (intra
coded MBs generally use the most bits).
17. View frames 35, 36 and 37, as shown in Figure 14. Observe that the
MacroBlocks disappear.
18. Go back to frame 34.
19. From the Overlay menu, click MB Statistics, and then click Bits.In
Figure 15, note that the black background uses a high number of bits.
20. View frames 35, 36 and 37, as shown in Figure 16. Observe that the
background uses progressively fewer bits.
21. Compare frame 34 with frame 37. Observe that the black background in
frame 34 is coded and uses many bits, while the black background in frame
37 is not coded, and it uses no bits.
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 2: MPEG--4 Compliance
Figure 13: Frame 34, color key
Figure 14: Frames 35, 36, and 37, color key
Figure 15: Frame 34
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MTS4CC Elementary Stream Compliance Checker Tutorials
Figure 16: Frames 35, 36 and 37
Conclusions
Tutorial 2: MPEG--4 Compliance
This tutorial demonstrated how to:
Additional Information
Covered
H Use and interpret the alert pop-up messages.
H Use the Video summary tooltip and understand the information provided.
H Use the MacroBlock overlays: MB types and motion vectors.
H Use the hexview bitstream viewer.
It appears that the encoder chooses MB types less than optimally by using intra
MBs for the background, which wastes many bits.
H Consider whether there are software bugs, such that the encoder is too
sensitive to minor changes in the gray level.
H Check the encoder part of the codec that decides when to use Intra MBs and
Inter MBs, and when to not code the MB.
Fixing this problem would save many wasted data bits.
NOTE. The MPEG-4 standard provides more data bits for intensity-gray level
than for color information, so it is naturally more sensitive to changes in gray
level (this mimics the human visual system). However, it appears that the
sensitivity to gray in this example is too great.
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Tutorial 2: MPEG--4 Compliance
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 3: MP4 Compliance Basics
This tutorial covers the following:
H Opening an MP4 file and viewing the tracks.
H Syntax error: not obeying Profile/Level restrictions.
H Extracting and saving the video track.
H Viewing MP4 file structure.
This tutorial requires that you have completed the previous tutorials and that you
can perform the following tasks:
H Play, stop, step forward, and fast forward a video.
H Use and interpret the alert messages.
H Use the Video summary tooltip and understand the provided informa-
tion.
H Use the MacroBlock overlays: MB types and motion vectors.
Procedure
H Use the hexview bitstream viewer.
1. To load the MP4 tutorial, click File > Example files > MP4 Files> Packet
Woman. A list of tracks included in the MP4 appears in a dialog box, as
shown in Figure 17.
2. View the track information included in the dialog box. The video track ID,
for example, is 001. Although there can be multiple tracks, the first video
track is selected automatically.
3. Click OK. The video track is analyzed, and an error message appears, as
shown in Figure 18.
4. View the error message details as shown in Figure 18:
H The VOP has more MacroBlocks (396) than allowed in MPEG-4 /
Simple Profile / Level 1: the maximum number allowed is 99.
H This is likely an error with the level. It is stated as Level 1 in the
encoded file, but it is actually the size of a Level 2.
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 3: MP4 Compliance Basics
Figure 17: Track list
Figure 18: Initial error message
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 3: MP4 Compliance Basics
5. Select Skip this Error only in the future, and then click Continue.
MTS4CC will continue, by using the actual size. A buffer conformance
warning message appears, as shown in Figure 19.
6. View the warning message details as shown in Figure 19:
H Overflow by 297 MB.
H This error is to be expected, because the Level is incorrectly given as L1
(which has a limit of 99 MBs) whereas it should be L2 (which has a
limit of 396 MBs).
Figure 19: VCV overflow warning message
7. Select Skip this Warning only in the future, and then click Continue.
Another buffer conformance warning message appears, as shown in
Figure 20.
8. Select Skip this Warning only in the future, and then click Continue.
9. To ensure that the application window is active, click the Title bar.
10. From the analysis menu, select View video stream structure.TheStruc-
ture window appears, as shown in Figure 21.
11. View the top-level atoms in the MP4 file. Click the + next to each atom to
view the data for the atom.
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Tutorial 3: MP4 Compliance Basics
Figure 20: VBV underflow warning
20
Figure 21: Structure window
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 3: MP4 Compliance Basics
12. From the File menu, click Close stream, and then reopen the stream.
13. When the track list appears, click Extract, as shown in Figure 22. The Save
stream file as dialog box appears, as shown in Figure 23.
Figure 22: Track list
Figure 23: Save stream file as dialog box
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 3: MP4 Compliance Basics
14. In the Save stream file as dialog box, type a different file name if required.
NOTE. To open this dialog box in the future for a video track that was not
extracted at the time the MP4 file was first opened, open the File menu and then
click Save stream file as.
Conclusion
This tutorial demonstrated how to:
H View the tracks in an MP4 file.
H Extract and play a video, while checking for errors.
The track ID and video file type has been automatically appended to the file
name.
H Identify and locate the Level conformance error.
H Identify two buffer conformance errors (see Tutorial 5 for details about
buffer analysis).
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 4: MP4 Optimization
This tutorial covers the following:
H Opening an MP4 file and viewing the video track.
H Using the Video summary tooltip and the MB types overlay.
H Performing optimization checks that could reduce bit usage by 45% in this
sequence.
This tutorial requires that you have completed the previous tutorials, and that
you know how to:
H Play, stop, step forward, and fast forward the video.
H Use and interpret the pop-up alerts.
H Use the Video summary tooltip and understand the information provided.
H Use the MacroBlock overlays: MB types and motion vectors.
H Use the hexview bitstream viewer.
Procedure
H Open MP4 files, view/extract the video, and view the MP4 file structure.
1. To load the MP4 tutorial, click File > Example files > MP4 Files>
Picadilly Circus. A list of tracks included in the MP4 appears in a dialog
box, as shown in Figure 24.
2. View the track information included in the dialog box. The video track ID,
for example, is 001. Although there can be multiple tracks, the first video
track is selected automatically.
3. Click OK.
4. To view the Video Summary tooltip, click the
5. To view the MB types overlay, click the icon or type CTRL + M.
6. Click the
shown in Figure 25.
icon. A VCV buffer conformance warning message appears, as
icon or type CTRL + U.
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 4: MP4 Optimization
Figure 24: Track list
24
Figure 25: VCV buffer conformance warning message
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 4: MP4 Optimization
7. Select Skip this Warning only in the future, and then click Continue.
8. View the progression of frames, and note that the first frame is green, as is
every third frame (Intra MBs), as shown in Figure 26. Another buffer
conformance warning message appears, as shown in Figure 27.
Figure 26: Progression of frames
Figure 27: VBV underflow warning
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 4: MP4 Optimization
9. Select Skip this Warning only in the future, and then click Continue.
10. To replay the video file, click Pause, step forward. Note that the first frame
takes 32,456 bits, as shown in Figure 28.
Figure 28: Frame 1
26
11. Click the red close button to remove the MB Types Key window.
12. Click the
13. To undock the MB Types Key window, hold the CTRL key, while dragging
it with the mouse pointer.
14. View the next six frames, including Frame 2, which is shown in Figure 29.
15. For each frame, view the details, which are outlined in Table 3.
icon twice to reopen the MB Types Key window.
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 4: MP4 Optimization
Figure 29: Frame 2
Table 3: Frame details
Frame Frame type Bits used
2 P-VOP 7,208
3 P-VOP 7,792
4 I-VOP 33,152
5 P-VOP 7,216
6 P-VOP 8,776
7 I-VOP 34,344
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Tutorial 4: MP4 Optimization
Conclusion
This tutorial demonstrated the following:
H The I-VOPs require about 4.5 times as many bits as the P-VOPs.
H There are I-VOPs every 3rd frame.
H There is no need to have I-VOPs so often. If the frequency of I-VOPs were
reduced to 1 in 30, the bits used for the sequence would reduce by ~45%.
H You can reduce the number of bits used.
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 5: MPEG-4 and H.264/AVC Buffer Analysis
This tutorial covers the following:
H Buffer analysis in real-time (VBV, VCV, VMV of MPEG-4 ES).
H Information provided -- values, overflow/underflow indications.
H Icon controls for navigation through the graphs.
H Buffer conformance errors/alerts.
H Graphs.
H Error dialog boxes.
H Achieving conformance.
H Altering the buffer parameters and seeing the effect in the graph.
H Adjusting values to prevent overflow.
H HRD buffer analysis in H.264/AVC.
This tutorial requires that you have completed the previous tutorials, and that
you know how to:
H Play, stop, step forward, and fast forward a video.
H Use and interpret the alert messages.
This tutorial also requires that you already understand the principles of buffer
analysis/conformance (VBV, VCV, VMV) in MPEG-4 and H.264/AVC (HRD).
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
Table 4 provides the functions of each Buffer Analysis toolbar icon.
Table 4: Buffer analysis icons
Icon Function
Zoom in (+) and zoom out (--) centered on the window;
affected by the Lock X / Y icons.
Fit all data into window.
Go to origin (zero), which is the start of the video sequence.
Lock X/Y zoom in/out and scrolling/panning. When the Lock
Y button is pressed, zoom in and zoom out and scroll/pan only
affect the X-direction. This allows you to keep a useful vertical
scale, while still viewing the length of the video sequence.
Autoscroll; fill the analysis data in real time as the video is
being decoded and scroll the window to the right.
Procedure
Measure the data at the cursor. The data values are reported on
the status line at the bottom of the analysis window. Offsets
and angles/slopes of lines can also be measured by holding the
mouse and dragging.
Scroll/pan (the cursor changes to show the scroll/pan direction); this is affected by the Lock X-Y icons.
Zoom in/zoom out centered on the location of this cursor; this
is affected by the Lock X-Y icons. Press the <shift> key to
zoom out.
1. To load the tutorial, click File > Example files > MPEG-4 Elementary
Streams> Man Walking. Ensure that the video is not playing.
2. From the Analysis menu, click View buffer analysis.TheBuffer Analysis
window appears, as shown in Figure 30.
3. View the graph example in Figure 30, as well as the descriptions in Table 5.
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
1 2 3
12
11
10
Figure 30: Buffer analysis window, example gr aph
Table 5: Buffer analysis descriptions
4
5
9 8 7 6
Area Description
1 Graph window control toolbar.
2 Frame type, number.
3 Graph window.
4 List of analyses for VBV, VCV, and VMV.
5 Location of overflows and underflows in stream.
6 Scroll bar for sequence.
7 Time through sequence.
8 Vertical blue line at time=0; vertical gray lines at each VOP decode time.
9 Status lines.
10 Custom values.
11 Switch on/off VBV, VCV, VMV graphs
12 Source of buffer analysis values
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
4. Observe the VBV, VCV and VMV values that appear beside the graph and
are shown in Figure 31. These parameters are specified in the stream, or
from the implied values from the Profile/Level, as given in the standard, or
the implied values from the Object Type (Simple or Advanced Simple), at
the highest level for each. You can enter them manually by selecting Use
custom parameters.
Figure 31: VBV, VCV and VMV values
5. Click the Pause/ Step Forward icon
the window because the Man W alking sequence contains B-VOPs, and the
buffer analysis cannot start until there is sufficient data for the calculations
(this will not occur until frame 4).
6. Click the Pause/ Step Forward icon
7. Click the Fit to Window icon
shown in Figure 32.
8. Click the Fast forward icon
Figure 33.
9. Note that the VBV overflow occured while decoding frame 55 (the display
frame number is 54).
for a more detailed view of the graph, as
. A warning message occurs, as shown in
three times. Nothing appears in
one more time. The graph appears.
32
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
Figure 32: Buffer analysis graph, detailed view
Figure 33: VBV overflow warning
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
10. Select Skip this Warning only in the future, and then click Continue.
11. Observe that the red VBV line goes above the Buffer limit line, as shown in
Figure 34.
12. Observe that when the decoding stops, the graph looks like the section that
appears between 75% and 105% buffer occupancy. Note also that the number
of frames with VBV overflow appears at the bottom of the screen. In this
case, the number of frames with VBV overflow is 106.
34
Figure 34: Buffer limit graph
13. To fit the graph to the window, click the
toolbar. The red line displays the VBV overflow, as shown in Figure 35.
MTS4CC Elementary Stream Compliance Checker Tutorials
icon on the Buffer Analysis
Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
Figure 35: Comparitive video verifier graph
14. Consider the information presented by the graph. The standard values used
for a frame result in a VBV overflow, which means that the decoding rate
cannot keep up with the input data rate, and frames will drop, beginning with
frame 54.
Solutions include:
H Increase the vbv_buffer_size so that it does not overflow.
H Decrease the bit-rate, which is the rate at which the encoder sends the
data to the decoder.
H Increase the displayed frame rate, so that the decoder removes bits more
quickly.
H Increase the number of bits per frame by changing the quantizer or
increasing the frame size.
H Change the Profile/Level indication, so that it stays within the set limits
(for example, change to ASP at Level 2).
H Use custom values in the vbv_parameters in the sequence header.
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
15. Clear the check boxes for VCV and VMV so that only the VBV check box is
selected. Note that the vertical scale is now measured in bits, not %, as
shown in Figure 36.
16. Observe that the VBV line has disappeared because it is beyond the scale set
for the VBV.
17. Click the
icon three times for a detailed view of the graph, as shown in Figure 37.
icon on the Buffer Analysis toolbar, and then click the
Figure 36: Frame 2
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
Figure 37: Graph details
18. Note the following details about the graph:
H The Y scale of the graph is locked, which keeps the graph at a useful
zoom level.
H The VBV graph is higher at the end of every frame than at the start,
which shows that the VBV buffer is filling faster than the decoder can
empty it.
19. Click the
20. Select the Use custom parameters option button, as shown in Figure 38.
The word BUF appears in a yellow box in the main MTS4CC status bar,
indicating that custom buffer parameters are in use, as shown in Figure 39.
icon to zoom out.
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
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Figure 38: Buffer analysis configurations
Figure 39: Buffer parameter indicator
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
21. View the video buffer verifier, as shown in Figure 40. The default vbv_buffer_size for ASP L0 is 163,840 bits = 20,480 bytes, which is not very large.
22. Enter 655,360 bits = 80 kbytes, click Apply, and then click the Fit to
window icon
no overflows or underflows.
23. Consider the following:
H What if your mobile device cannot spare 80 KBs of memory, and can
only spare 20 KBs, as specified by the standard?
H By how much does the input data rate need to be reduced?
H Does this comply with the specifications of the network on which your
device will operate?
. Observe that the graph stays below the limit and there are
Figure 40: Video buffer verifier graph
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
24. Reset the parameters by clicking Use parameters from stream header,and
then reselect the Use custom parameters check box. The VBV graph shows
that the decoder is being supplied with data faster than it can decode.
25. Reduce the bit rate to 121072 bits, as shown in Figure 41, and then click
Apply. The graph goes up slightly and there are fewer frames with overflow,
as shown in Figure 42.
Figure 41: Bit rate configurations
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Figure 42: Video buffer verifier graph
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
26. Reduce the bit rate to 111072 bits, as shown in Figure 43, and then click
Apply.
27. Observe that the graph line now stays below the buffer limit, as shown in
Figure 44.
28. Consider whether the maximum rate of 111,072 bits meets your network’s
specifications.
Figure 43: Video buffer verifier configutations
Figure 44: Video buffer verifier graph
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Tutorial 5: MPEG--4 and H.264/AVC Buffer Analysis
Conclusion
This tutorial demonstrated that the buffer analysis of the MPEG-4 example, Man
Walking, showed that the stream does not comply with the buffer constraints.
The tutorial recommended ways to resolve this issue.
The tutorial also brought up the following considerations:
H How much memory needs to be allocated? Can your hardware allow this
much memory usage?
H Is the input data rate limit appropriate for your network?
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 6: MPEG-2 Compliance
This tutorial covers the following:
H Opening an MPEG-2 program stream.
H Interpreting syntax errors:
H Person track: invalid VLC for dct_differential.
H Grenadier guards: frame_rate_extension denominator and numerator
equal but not zero.
H Using the HexView:
H Going from the alert pop-up to the HexView.
H Examining the bitstream in the HexView.
H Looking at the MPEG-2 program stream structure.
H Looking at MacroBlock types in an interlaced video.
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Tutorial 6: MPEG-2 Compliance
Procedure
1. To load this tutorial, click File > Example files > MPEG-2 Program
Streams> Person Track. A list of tracks included in the MPEG-2 program
stream appears in a dialog box, as shown in Figure 45.
2. View the track information included in the dialog box. The video track ID,
for example, is 0xe0. Although there can be multiple tracks, the first video
track is selected automatically.
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Figure 45: Track list
3. Click OK. The video track is analyzed and an error appears, as shown in
Figure 46.
4. View the error message details, which provide a summary of the stream up to
the point of the error.
5. Click Continue. Ensure that the Skip this Error only in the future check
box is not selected. Another buffer conformance error message appears, as
shown in Figure 47.
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 6: MPEG-2 Compliance
Figure 46: Initial error message
Figure 47: Invalid VLC error message
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Tutorial 6: MPEG-2 Compliance
6. View the error message details. An invalid VLC has been used for the
dct_differential field at bitstream byte address 0x1000, bit 5.
7. Click Continue. Ensure that the Skip this Error only in the future check
box is not selected. Repeat this step for an additional error message that
appears.
8. Resume playing the video. Observe that the error is visible in frame 1, as
shown in Figure 48.
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Figure 48: Error in image
9. Click the the Pause, Step forward icon
10. Click Continue. An Invalid VLC error message appears, as shown in
Figure 49.
11. From the Goto menu, click Hex.
12. Click Continue, and then view the HexView window, as shown in
Figure 50. Note that the error is highlighted automatically.
13. Observe the bits surrounding the error and consider whether it is a start code
emulation.
MTS4CC Elementary Stream Compliance Checker Tutorials
. An error message appears.
Tutorial 6: MPEG-2 Compliance
Figure 50: HexView window
Figure 49: Invalid VLC error message
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Tutorial 6: MPEG-2 Compliance
14. To open the Grenadier Guards program stream, Click File > Example files >
MPEG-2 Program Streams> Grenadier Guards. An error message
appears, as shown in Figure 51.
15. View the details of the error message: the value of the denominator of
frame_rate_extension is 1, but it must be 0 in Main Profile.
Figure 51: Error message
16. Select Skip this Error only in the future, and then click Continue.The
status bar indicates one disabled alert, as shown in Figure 52. An error
message and a warning message appear, as shown in Figure 53 and
Figure 54.
Figure 52: Disabled alert indicator
17. For both error messages, select Skip this Error or Warning in the future,
andthenclickContinue. Do not resume playing the video.
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MTS4CC Elementary Stream Compliance Checker Tutorials
Figure 53: Error message
Tutorial 6: MPEG-2 Compliance
Figure 54: Warning message
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Tutorial 6: MPEG-2 Compliance
18. From the Analysis menu, select View video stream structure.The
Structure window appears, as shown in Figure 55.
19. View the top-level atoms in the MPEG-2 program stream. Click the + next to
each atom to view the data for the atom.
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Figure 55: Structure window
20. Resume playing the video. The Interlace toolbar appears, as shown in
Figure 56.
Figure 56: Interlace toolbar
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 6: MPEG-2 Compliance
21. Click the Pause, Step Forward icon
to view frame 2.
22. On the Interlace toolbar, click the Split fields view icon
bottom fields are displayed separately, as shown in Figure 57.
Top
Bottom
. The top and
Figure 57: Frame 2
23. Maximize the video window.
24. Click the
icon. Different MB types appear in the top and bottom fields,
as shown in Figure 58.
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Tutorial 6: MPEG-2 Compliance
Top
Bottom
Conclusion
Figure 58: Varied MB types
This tutorial demonstrated the following:
H There is one error in the Person Track stream:
H The error is frame 1, at bitstream location 0x1000, bit start 5.
H This error affects the visual quality.
H There are two errors and one warning message in the Grenadier Guards
stream:
H The errors are in the header (before frame 1), at bitstream location 0x15,
bit start 6.
H The warning message highlights the same error.
H This does not appear to affect the visual quality.
H You can see the different MacroBlock types in the top and bottom fields.
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 7: Fidelity Analysis
This tutorial covers the following:
H Fidelity analysis in real-time (PSNR).
H Using a YUV source reference file.
H Fidelity metrics.
H Graph navigation.
H Comparing the fidelity of the same bitstream compressed with either
MPEG-2 or H.264/AVC.
H Viewing the visual difference between the compressed bitstream and the
YUV source reference video.
This tutorial requires that you have completed the previous tutorials and that you
can:
H Open example streams.
H Play, stop, step forward, and rewind a video.
Procedure
H Use and interpret alert pop-up messages.
H Use the icons and controls on the buffer analysis graphical display.
This tutorial also requires that you already understand the principles of fidelity
analysis (MTS4CC does not cover this; however, the user manual contains
descriptions of the fidelity metrics).
1. To load the tutorial, click File > Example files > MPEG-4 Elementary
Streams> Man Walking. Ensure that the video is not playing.
2. From the Analysis menu, click Enable fidelity analysis.TheVideo
analysis options dialog box appears (see Figure 59) for theYUV reference
file. This file will later be used for comparison with the compressed video
file. The YUV reference file is provided as an example, as indicated by the
text under the Reference filename field, shown in Figure 59.
3. Set the Frame rate to 30, as shown in Figure 59.
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Tutorial 7: Fidelity Analysis
Figure 59: Video analysis options
4. From the Metric drop-down menu, select PSNR (full signal range),and
then click OK. (A detailed description of each fidelity metric is available in
the user manual).
5. From the Analysis menu, click Enable fidelity trace.
6. On the Trace tab, select the Enable check box, choose the filename
mp4asp_1_video and then, under Options, select VOP Fidelity, as shown
in Figure 60.
7. On the Frame range tab, select the All frames check box, as shown in
Figure 61, and then click OK. The video window appears with the fidelity
analysis icon
enabled in the Views toolbar.
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 7: Fidelity Analysis
Figure 60: Video analysis options
Figure 61: Frame range tab
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Tutorial 7: Fidelity Analysis
8. Click the Fidelity analysis icon
appears, as shown in Figure 62. Observe that the graph is empty because a
video has not been played.
9. Click the
10. Observe the following about the graph shown in Figure 63:
H The graph area is not filled with each click because the bitstream
includes B-VOPS, and a certain number of frames must be decoded
before each frame can be displayed.
H Some of the YUV PSNR values are not visible. This is because the
graph auto-scales with the first few values. You can click the
rescale the graph.
H The thumbnail bar view shows that the fidelity data has been collected.
11. View the descriptions of the Fidelity analysis window, as shown in
Figure 64 and Table 6.
icon four times. A graph appears, as shown in Figure 63.
.TheFidelity analysis graph view
icon to
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 7: Fidelity Analysis
Figure 62: Fidelity analysis graph
Figure 63: Fidelity analysis graph
MTS4CC Elementary Stream Compliance Checker Tutorials
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Tutorial 7: Fidelity Analysis
9
1
8
2
7
6
3
5
4
Figure 64: Fidelity analysis window descriptions
Table 6: Fidelity analysis window descriptions
Area Description
1 Graph window
2 YUV color key
3 Scroll bar; appears and disappears according to zoom scale
4 Time through sequence
5 Status line; display measurements
6 Thumbnail bar line; displays overview
7 Vertical blue line at time=0; vertical gray lines at each VOP decode time
8 Frame type, number
9 Graph window control toolbar
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MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 7: Fidelity Analysis
12. To open the Grenadier Guards program stream, Click File > Example files >
MPEG-2 Program Streams> Grenadier Guards. An error message
appears.
13. Select Skip this Error only in the future, and then click Continue.
14. From the Analysis menu, select View analysis options.
15. On the Visual difference/ Fidelity tab, set the YUV frame rate to 25, and
then click OK.
16. An error message appears because there are only 10 frames of YUV data.
Click OK, and then view the graph result, as shown in Figure 65.
17. Load the MPEG-2 program stream example, Grenadier Guards, as shown in
Figure 66.
18. Compare the MPEG-2 program stream in Figure 66 with the H.264/AVC
PSNR example shown in Figure 67. Note that the PSNR is higher for
H.264/AVC in Y, U, and V.
Figure 65: Graph result, YUV frame rate 25
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Tutorial 7: Fidelity Analysis
Figure 66: MPEG- 2 program str eam, Grenadier Guards
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Figure 67: H.264/AVC stream, Grenadier Guards
MTS4CC Elementary Stream Compliance Checker Tutorials
Tutorial 7: Fidelity Analysis
19. Click the View trace icon as shown in Figure 68.
Figure 68: View trace icon
20. The trace view gives the numerical values for the pictures’ PSNR, as shown
in Figure 69.
21. Consider the following:
H What encoder parameters, such as frame type, were used for H.264/AVC
and MPEG-2?
H Could the H.264/AVC or the MPEG-2 encoding parameters be changed
to improve the areas of lower PSNR?
H Compare other fidelity analyses; do the same kinds of differences occur?
H Although the PSNR is better for the H.264/AVC sequence, it does not
necessarily look better. Consider the visual differences.
Figure 69: H.264/AVC sequence
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Tutorial 7: Fidelity Analysis
22. Load the MPEG-2 stream, Grenadier Guards.
23. From the Overlay menu, click Visual difference, and then select the Enable
check box.
24. Set the Frame rate to 25, and then click OK.TheVisual difference toolbar
appears.
25. Use the following icons to view the visual difference.
Table 7: Visual difference icons
Icon Function
View encoded
View YUV reference
View difference
Conclusion
View luma only (not U or V)
26. Load the H.264/AVC stream, Grenadier Guards. Consider whether there is a
difference in visual quality between the two streams.
This tutorial demonstrated the following:
H A method for assessing visual quality through:
H The use of metrics such as PSNR.
H Identifying the visual difference between the encoded video and the
reference (source) video that is used for the encoding.
H Visual quality analysis and visual quality improvement require that you
consider encoding parameters (such as frame types and motion vectors) and
bit--rates of encoding.
This tutorial provided the tools to help you begin your visual analysis in a
quantifiable and logical fashion.
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MTS4CC Elementary Stream Compliance Checker Tutorials
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