[Ffmpeg-devel] ISO MPEG4 VO header description? (original) (raw)

Bill May wmay
Wed Feb 8 21:59:47 CET 2006

Patrice Roulet wrote:

Hi

I would like to know if anybody could explain me the VO header in ISO MPEG 4. I receive a MPEG 4 streamming frames and I need to generate VO header to put it in AVCodecContext::extradata I have only the width and height. Which values should I set to profile, frameRate, shortTime, variableRate and quantType.

Mpeg4 has several headers that give information about the encoding used in the stream.

The VO, VOL, VOSH all have information that can be used; the VOL is the key piece to the puzzle.

These are described in ISO/IEC14496-2, section 6.2.3 (Video Object layer).

If you're streaming using RTP, these fields (as hex digits) should be located in the SDP in the a=fmtp statement, config= heading. For RFC3016, those fields are not included in the stream.

If you're doing something else, you'll have to parse for those; for decoding with ffmpeg, you should pass them first to the decode, and will be the generated in the first encoded frame.

Bill

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