[Libav-user] Format in which ES data is stored in (AVPacket*) pkt->data buffers

[Sergey Fedorov]

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!
>
> Anshul
> 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
>> Arvind
>>
>>
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>>
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