New tool to change SAR in H264 bitstream

Originally Posted by reinen

I also tried to lower the reference frames from 16 to 4

Only way of doing that is via transcoding, changing a number in the header won't affect how many reference frames appear in the physical video stream ....

7ek

[LRN]

There's a problem with this fork. At http colon slash slash lrn.no-ip.info/other/wb_100/wb_100.tar.xz you can grab:
ffmpeg.exe - the remuxer i've used.
wb_100.264 - original sequence encoded with x264 without any SAR changes. Recognized as valid h.264 stream.
wb_100_x264_sar.264 - original sequence encoded with x264 with --sar 64:45 option. Recognized as valid h.264 stream.
wb_100_fixed.264 - a result of running `ffmpeg.exe -i wb_100.264 -vcodec copy -vbsf h264_changesps=sar=64:45 wb_100_fixed.264' . It is not regognized as valid h.264 stream
With a hex editor i was able to fix wb_100_fixed.264 by changing 3rd byte from 0x1D to 0x01 (so that it matches wb_100_x264_sar.264 and wb_100.264). I have not bothered to debug the fork to find why this byte changes suddenly.

[b66pak]

@LRN have you tested for other arguments too? (fps, level, crop, etc)...
_

[LRN]

No, i did not.
I did test it with different combinations of sar. For example, it produces valid file when invoked with sar=4:3 (or was it 5:4? i don't remember).

[roozhou]

My bad. Because 64:45 is not in H264's pre-defined SAR list(while 4:3 is), setting to such SAR value will change the length of SPS. For MP4 style bitstream, there is a 4-byte field before each nal telling the size of the nal. The filter tries to modify it even if the bitstream is AnnexB which has no such bytes.
This bug will be fixed in next release.

P.S. mplayer/ffmpeg's svn server is blocking all IPs from China mainland and Hong Kong. It is now difficult for me to sync to the latest ffmpeg code.
Further worse, sf.net has reset passwords for all users by email and unfortunately my email address registered on sf.net is no longer available. I can neither upload code nor release files.

[nm]

Originally Posted by roozhou

P.S. mplayer/ffmpeg's svn server is blocking all IPs from China mainland and Hong Kong. It is now difficult for me to sync to the latest ffmpeg code.

Does the same happen with the git repository?

[roozhou]

Originally Posted by nm

Does the same happen with the git repository?

git is OK

[bernd_b]

I wanted a h264-video being 23.976 fps becoming 24fps:

ffmpeg.exe -i Monk.S07E01_conv.mkv -vcodec copy -acodec copy -vbsf h264_changesps=fps=24000:1000 Monk.S07E01_video.mkv

But mediainfo still indicates me, that only the container has turned into 24 fps, there is still the information of the h264-stream to be 23,976 fps - or am I on the wrong track here:

mediainfo Monk.S07E01_video.mkv 
General
Unique ID                        : 302061734355895109743642512766325178364 (0xE33EF953255B3DC619A6ADC0A4D33FFC)
Complete name                    : Monk.S07E01_video.mkv
Format                           : Matroska
File size                        : 1.34 GiB
Duration                         : 43mn 7s
Overall bit rate                 : 4 456 Kbps
Writing application              : Lavf52.92.0
Writing library                  : Lavf52.92.0

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L3.1
Format settings, CABAC           : No
Format settings, ReFrames        : 2 frames
Codec ID                         : V_MPEG4/ISO/AVC
Duration                         : 43mn 7s
Bit rate mode                    : Variable
Bit rate                         : 3 919 Kbps
Maximum bit rate                 : 2 097 Kbps
Width                            : 1 280 pixels
Height                           : 720 pixels
Display aspect ratio             : 16:9
Frame rate                       : 24.000 fps
Original frame rate              : 23.976 fps
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.177
Stream size                      : 1.18 GiB (88%)
Language                         : English
Color primaries                  : BT.709-5, BT.1361, IEC 61966-2-4, SMPTE RP177
Transfer characteristics         : BT.709-5, BT.1361
Matrix coefficients              : BT.709-5, BT.1361, IEC 61966-2-4 709, SMPTE RP177

Audio
ID                               : 2
Format                           : AC-3
Format/Info                      : Audio Coding 3
Mode extension                   : CM (complete main)
Codec ID                         : A_AC3
Duration                         : 43mn 7s
Bit rate mode                    : Constant
Bit rate                         : 448 Kbps
Channel(s)                       : 6 channels
Channel positions                : Front: L C R, Side: L R, LFE
Sampling rate                    : 48.0 KHz
Bit depth                        : 16 bits
Compression mode                 : Lossy
Stream size                      : 138 MiB (10%)
Language                         : English

[roozhou]

@bernd_b
Add -muxerfps 24000/1001 to ffmpeg's parameters.

[bernd_b]

Thanks for your reply - but I am still stuck.

ffmpeg.exe -i Monk.S07E01_conv.mkv -muxerfps 24000/1001 -vcodec copy -acodec copy -vbsf h264_changesps=fps=24000:1000 Monk.S07E01_video.mkv

...

mediainfo Monk.S07E01_video.mkv
...
Display aspect ratio             : 16:9
Frame rate                       : 23.976 fps
Color space                      : YUV
...

Is it a problem that I actually use the windows version with wine under Linux?

Even If I try to transform the video alone I get the input and the output to be 23.976fps:

mediainfo Monk.S07E01_conv.h264
General
Complete name : Monk.S07E01_conv.h264
Format : AVC
Format/Info : Advanced Video Codec
File size : 1.21 GiB

Video
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings, CABAC : No
Format settings, ReFrames : 2 frames
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
...

wine ffmpeg.exe -i Monk.S07E01_conv.h264 -vcodec copy -acodec copy -vbsf h264_changesps=fps=24000:1000 Monk.S07E01_video.h264

...

FFmpeg version SVN-r26292, Copyright (c) 2000-2011 the FFmpeg developers
built on Jan 24 2011 20:49:50 with gcc 4.4.5
configuration:
libavutil 50.36. 0 / 50.36. 0
libavcore 0.16. 0 / 0.16. 0
libavcodec 52.108. 0 / 52.108. 0
libavformat 52.92. 0 / 52.92. 0
libavdevice 52. 2. 3 / 52. 2. 3
libswscale 0.12. 0 / 0.12. 0
[h264 @ 00120470] max_analyze_duration reached
[h264 @ 00120470] Estimating duration from bitrate, this may be inaccurate

Seems stream 0 codec frame rate differs from container frame rate: 47.95 (48000/1001) -> 23.98 (48000/2002)
Input #0, h264, from 'Monk.S07E01_conv.h264':
Duration: N/A, bitrate: N/A
Stream #0.0: Video: h264, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1200k tbn, 47.95 tbc
fixme:msvcrt:MSVCRT__sopen_s : pmode 0x01b6 ignored
Output #0, h264, to 'Monk.S07E01_video.h264':
Metadata:
encoder : Lavf52.92.0
Stream #0.0: Video: [0][0][0][0] / 0x0000, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], q=0-0, 90k tbn, 23.98 tbc
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
frame=62102 fps=971 q=-1.0 Lsize= 1264842kB time=2590.11 bitrate=4000.4kbps
video:1264842kB audio:0kB global headers:0kB muxing overhead 0.000000%


mediainfo Monk.S07E01_video.h264
General
Complete name : Monk.S07E01_video.h264
Format : AVC
Format/Info : Advanced Video Codec
File size : 1.21 GiB

Video
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings, CABAC : No
Format settings, ReFrames : 2 frames
Bit rate mode : Variable
Maximum bit rate : 2 097 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
...

[chompy]

Could this tool be used to "repair" DTS of a h264 stream (DTS of AU is not greater than DTS of previous AU), that is, is there a way to remove all DTS, and then correctly regenerate them again?

Greetings

EDIT:

Originally Posted by roozhou

MKV contains only PTS while MP4/FLV require both PTS and DTS. FFmpeg currently lacks the ability to generate DTS based on PTS. I have done some hack on the MKV demuxer so my ffmpeg generates correct DTS from MKV. That's why only my ffmpeg works on MKV.

I've tried H264 -> mkv -> H264 but the resulting file doesn't work, what should I do? Maybe H264 -> mkv -> mp4 -> H264? Or this DTS generation only works on containers but not on raw streams?

[roozhou]

Originally Posted by chompy

Could this tool be used to "repair" DTS of a h264 stream (DTS of AU is not greater than DTS of previous AU), that is, is there a way to remove all DTS, and then correctly regenerate them again?
Greetings
EDIT:
I've tried H264 -> mkv -> H264 but the resulting file doesn't work, what should I do? Maybe H264 -> mkv -> mp4 -> H264? Or this DTS generation only works on containers but not on raw streams?

Sorry, my tool only modifies SPS and nothing else in H264 bitstream.

[roozhou]

New build available.

@LRN
bug fixed.

[b66pak]

thanks a lot...
_

L.E. is not working for me...a line like this is a deadlock!

ffmpeg -i sample.mkv -vcodec copy -an -sn sample.mp4

_

[roozhou]

Originally Posted by b66pak

thanks a lot...
_

L.E. is not working for me...a line like this is a deadlock!

ffmpeg -i sample.mkv -vcodec copy -an -sn sample.mp4

_

I have no idea where does this problem come. I was using git branch from videolan. Plz download the new build which I build from the official git branch.

[b66pak]

now its ok...thanks a lot...
_

[sneaker_ger]

How to correctly crop 1088 to 1080?

I tried:

ffmpeg -i 1088.h264 -vcodec copy -an -vbsf h264_changesps=crop=0:8 1080.h264

But mkvmerge still detects 1088 lines and mediainfo says the following about the output:

Width                            : 1 920 pixels
Height                           : 1 088 pixels
Original height                  : 1 080 pixels

[Audionut]

You cannot crop without recoding.

[sneaker_ger]

Originally Posted by Audionut

You cannot crop without recoding.

I'm certainly not sure, but I don't think it is true for all cases - at least 1088 to 1080 should be possible, because H.264 works with mod16 resolutions internally anyways. I think that there may also be a SPS for the resolution which also needs to be changed and this feature might be missing at the moment.

[Audionut]

Originally Posted by sneaker_ger

at least 1088 to 1080 should be possible, because H.264 works with mod16 resolutions internally anyways.

Blu-ray 1088 is cropped to 1080 by the decoder.

When x264 adds lines to bring content to mod16 for encoding, the decoder crops that information at playback.

If you want to actually remove (crop) lines of resolution from the source. You will have to re-encode.