[gst-devel] Caps provided by parsers

[Marco Ballesio]

Hi Mikko,

On Fri, Nov 19, 2010 at 10:33 AM, Mikko Hurskainen <
mikko.hurskainen at notava.com> wrote:

> Hi,
>
> There seems to different behaviour with different parsers what comes to
> the resolutions etc. E.g. for H.263 stream quicktime parser gives
> resolution and rtph263depay gives only stream type.


The h263 depayloader covers the functionalities as specified in rfc2190 (
http://www.faqs.org/rfcs/rfc2190.html) which afaik are not requiring to
extract information about the frame size. This information is usually
extracted from the decoder itself or carried within the container format /
signalling protocols.


> My codec requires these settings.


If you're using the decoder for an RTSP/VoIP session it's likely you got the
codec-data (aka sprop-parameters-set) during the signalling phase. If you're
getting them in-band you don't likely need a parser (and maybe you're
dealing with an under-performing decoder). I'm not 100% sure h263 carries
codec-data in band though :\ (note for me: read again ITU-T h263 specs).


> So the question is, should the parsing functionality be
> implemented by the codec or by parser in general ? Is there somewhere a
> description what is expected from a codec ?
>

Usually, the best place to process encoded data is within a decoder.
Processing it twice (e.g. first into a parser, then into a decoder) is, at
best, less efficient.

My personal opinion is that wherever you need a parser for a decoder to work
either you're working with a raw stream or with a broken decoder. In the
first case, it's better if either you payloaded or multipex your data, in
the second it's good if you get a better decoder ;).

Regards


>
>  -- Mikko
>
>
>
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