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Old 29th January 2010, 08:10   #1  |  Link
roozhou
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Join Date: Apr 2008
Posts: 1,181
New tool to change SAR in H264 bitstream

I write a bitstream filter for ffmpeg. It can modify sps in H264 bitstream. So far it can change sar, fps, crop information, level, ref frames, cfr/vfr flag, fullrange flag, colorprim, transfer and colormatrix. Since the length of bitstream may be changed, I cannot make an in-place modifier.

ffmpeg git 29946
Download from sf (win32 only)

Patches can be found on svn.

Note this is a demuxer/muxer only ffmpeg build.

cmdline:

ffmpeg -i infile -vcodec copy -acodec copy -vbsf h264_changesps=arg1[/arg2[/arg3]] outfile

args can be:
sar=x:y ---- Set sar to x:y, 0:0 will remove sar info
fps=x:y ---- Set fps to x/y in cfr mode or set timebase to y/x in vfr mode
level=x ---- Set level to x. (e.g. 30 for L3.0, 41 for L4.1)
crop=x:y ---- Crop x pixels from right and y pixels from bottom (e.g. 1920x1080 should use crop=0:8)
ref=x ---- Set number of reference frames to x
cfr ---- Set fps mode to cfr
vfr ---- Set fps mode to vfr
fullrange ---- Use full range (0~255)
limitedrange ---- Use limited range (16~235)

colorprim=x ---- Set color primary to x (integer)
1="bt709", 2="undef", 4="bt470m", 5="bt470bg", 6="smpte170m", 7="smpte240m", 8="film"

transfer=x ---- Set transfer to x (integer)
1="bt709", 2="undef", 4="bt470m", 5="bt470bg", 6="smpte170m", 7="smpte240m", 8="linear", 9="log100", 10="log316"

colormatrix=x ---- Set color matrix to x (integer)
0="GBR", 1="bt709", 2="undef", 4="fcc", 5="bt470bg", 6="smpte170m", 7="smpte240m", 8="YCgCo"

removesei ---- Remove SEI from bitstream. This can be used to remove user data and HRD timing info.
removeaud ---- Remove access unit delimiters, which is useless outside BD player.
removedupheader ---- Remove duplicated sps/pps. In some AnnexB bitstreams sps/pps appear in every I frame. We can safely remove them.

multiple args should be separated by /

Output format is determined by extension.
Supported input and output containers:
ts,mp4,mkv,flv --> mp4,mkv,flv
ts,mp4,mkv,flv --> raw,avi(with -vbsf h264_mp4toannexb)
raw,avi --> raw,avi

It also supports remuxing aac from adts/rm/mp4/mkv/avi to adts/mp4/mkv/avi, and you don't need -absf aac_adts2asc.

Two optional args are added to h264_mp4toannexb:
norepeatheader ---- Write sps/pps only in the first frame
avihack ---- Hack on nal start code, saving ~1 byte per frame on avi. It has no effect on raw output. Avihack implies norepeatheader

A new option -muxerfps is added to ffmpeg. Use this to set container fps for avi or default duration for mkv. This is useful for vfr video (e.g. 120000/1001 for 24/30/60 fps mixed content) or mp4/mkv/flv -> avi muxing.

Example:
convert avc in mkv to raw:
ffmpeg -i input.mkv -vcodec copy -an -vbsf h264_mp4toannexb=norepeatheader output.h264

convert avc in mp4 to avi, set container fps to 29.97:
ffmpeg -i input.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb=avihack -muxerfps 30000/1001 -vtag H264 output.avi

Another new option -bom can be used to add BOM to extracted text files(e.g. ass subtitles).

Example:
extract ass subtitle from mkv
ffmpeg -i input.mkv -vn -an -scodec copy -bom utf-8 output.ass

Last edited by roozhou; 15th August 2011 at 12:32.
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