I'm currently using ffmpeg to generate the elementary stream from an .mp4. I know that ffmpeg will not include the VOL header so I set about to generate the VOL. Now I seem to be able to generate the VOL header fine except that I need to know how to get one of the actual arguments passed into the method.
I was using this article I found on the TI Wiki to help build the VOL http://processors.wiki.ti.com/index.php/Extracting_MPEG-4_Elementary_Stream_from_MP4_Container
Here is the snippet of the article I need help with below
Use ffmpeg with the -vcodec copy option to extract the raw video codec data as it is.
$ ffmpeg -i test.mp4 -an -vcodec copy body.m4v
FFmpeg version SVN-rUNKNOWN, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-gpl --enable-pp --enable-swscaler --enable-pthreads --enable-libvorbis --enable-libtheora --enable-libogg --enable-libgsm --enable-dc1394 --disable-debug --enable-shared --prefix=/usr
libavutil version: 1d.49.3.0
libavcodec version: 1d.51.38.0
libavformat version: 1d.51.10.0
built on Mar 16 2009 21:16:26, gcc: 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 29.97 (30000/1001)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
Duration: 00:00:18.4, start: 0.000000, bitrate: 2089 kb/s
Stream #0.0(eng): Video: mpeg4, yuv420p, 640x480, 29.97 fps(r)
Output #0, m4v, to 'body.m4v':
Stream #0.0: Video: mpeg4, yuv420p, 640x480, q=2-31, 29.97 fps(c)
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
frame= 553 q=0.0 Lsize= 4703kB time=18.5 bitrate=2088.1kbits/s
video:4703kB audio:0kB global headers:0kB muxing overhead 0.000000%
You can get the vop_time_increment_resolution, video_object_layer_width and video_object_layer_height values from the FFmpeg message output to the console. You need to know these values to regenerate a VOL header at the next step. For the above example, you can read:
- vop_time_increment_resolution = 1000
- video_object_layer_width = 640
- video_object_layer_height = 480
The article mentions that the vop_time_increment_resolution is 1000... first since I am new to this ..what is the time increment resolution? Second, how do I get it since the only '1000' I see is part of the error message from ffmpeg and doesn't show up on the files I'm using :(
Is there a way of deriving this value from the other information present?
Thanks in advance,
Peter