[FFmpeg-devel] NC camera patch

[nicolas martin]

> nicolas martin wrote:
>
>> Hi all,
>>
>> I finally made some code to read the camera feed sent by NC46** types
>> cameras.
>>
>> Thanks for reading and sharing your thoughts !
>
> The format looks quite simple and your code quite complicated.
> Maybe I missed some subtlety in the format.
> So let me first describe the format as I understand it:
> Each frame is composed of:
>  - A header (16 bytes)
>    * 4 bytes : a flag (eg: 0x1A5  (big-endian))
>    * 1 byte  : unknown/unused
>    * 2 bytes : data_size (only when flag == 0x1A5)
>    * 9 bytes : unknown/unused
>  - MPEG4 data frame (data_size bytes)
> Please correct me if there's something wrong here.

Yeah, that's it !

>
>
> If my description is right, you could write your frame reader
> function trivially, with something like that:
>
>  flag = get_be32(pb);
>         get_byte(pb);
>  size = get_le16(pb);
>  url_fskip(pb, 9);
>  if (flag != 0x1A5)
>      /* error handling */;
>  av_new_packet(pkt, size)
>  get_buffer(pb, pkt->data, size);
>
> You need some more error checking, etc...
> But basically, this code should be enough.

Well you definitely have it ...
I didn't read a lot of code in ffmpeg, and so I thought I had to use  
get_partial_buffer at any cost.
Once you know, you can read as many bytes as you need, then definitely  
this code is way much simpler.

>
>
> BTW: you should upload a sample file like described in [1] to allow
> other developers to test your code.

I will do it !

> Oh, and your nc_read_header() seems to contain code which is
> totally unrelated to your format (MJPEG, DIRAC, etc...).
> And you don't need to use s->iformat->value if it's hardcoded
> to MPEG4.

I really don't know what to put there.
In fact, I copied a chunk of code, I found in raw.c.
The only thing I needed was to initialize my structure, that seems  
quite useless now !

So what should I put in it, now that I don't have to use a structure  
anymore ?

>
>
> Aurel
>
> [1] http://ffmpeg.org/bugreports.html
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