[Libav-user] Format in which ES data is stored in (AVPacket*) pkt->data buffers
night.rain.whisper at gmail.com
Fri Jun 14 06:20:14 CEST 2013
By the way, you can find the stream header in AVCodecContext::extradata
after avformat_find_stream_info() call.
2013/6/14 Sergey Fedorov <night.rain.whisper at gmail.com>
> H.264 Video Types<http://msdn.microsoft.com/en-us/library/windows/desktop/dd757808%28v=vs.85%29.aspx>:
>> The MP4 container format stores H.264 data without start codes. Instead,
>> each NALU is prefixed by a length field, which gives the length of the NALU
>> in bytes. The size of the length field can vary, but is typically 1, 2, or
>> 4 bytes.
> See also: H.264 extradata (partially) explained - for dummies<http://aviadr1.blogspot.ru/2010/05/h264-extradata-partially-explained-for.html>
> 2013/6/13 Anshul maheshwari <er.anshul.maheshwari at gmail.com>
>> U can try using gdb, put a brk point on above line u provided,
>> Print the pkt,
>> If trouble using gdb, reply me I wud do fr u!
>> It was never required to me!
>> On Jun 13, 2013 10:16 PM, "Arvind Raman" <arvind_raman at yahoo.com> wrote:
>>> Question - What is the format in which audio / video ES data is stored
>>> in (AVPacket*) pkt->data? I am trying to demux and decode AV data from
>>> a MP4 file using libavformat and libavcodec.
>>> More details
>>> 1. Using the sample application demuxing.c (
>>> http://www.ffmpeg.org/doxygen/trunk/demuxing_8c_source.html) I tried
>>> demuxing and decoding a MP4 file containing H.264 video and AACaudio.
>>> 2. While the sample application worked fine, I wasn't able to
>>> interpret the content in the pkt.data buffer (line #66 in the above file).
>>> Since the video was H.264 I was hoping to see familiar "nal_unit_type"
>>> but I don't think I saw that for the stream I was trying to decode. If I
>>> remember the data correctly the first 4 bytes in the pkt.data buffer were
>>> "0x00 0x00 0x02 0x72"
>>> I haven't spent much time figuring this out yet but searching on the
>>> Internet / forum didn't help. I intend to dig deeper tomorrow, but just
>>> wanted to check if indeed ES was being passed in the pkt.data buffers in a
>>> special way.
>>> Appreciate any points that you can provide.
>>> Best regards
>>> Libav-user mailing list
>>> Libav-user at ffmpeg.org
>> Libav-user mailing list
>> Libav-user at ffmpeg.org
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