[FFmpeg-devel] Ticket4753 question

[Paul B Mahol]

Dana 7. 8. 2015. 22:44 osoba "Ganesh Ajjanagadde" <gajjanag at mit.edu>
napisala je:
>
> On Fri, Aug 7, 2015 at 4:09 PM, Paul B Mahol <onemda at gmail.com> wrote:
> > On 8/7/15, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> >> On Fri, Aug 7, 2015 at 11:59 AM, Paul B Mahol <onemda at gmail.com> wrote:
> >>> On 8/7/15, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> >>>> https://trac.ffmpeg.org/ticket/4753:
> >>>> The issue seems to come from the fact that there are multiple frames
per
> >>>> packet.
> >>>> In fact, the duration field of the packet is set incorrectly,
> >>>> and reports the duration of a single frame only (80).
> >>>> Unfortunately, I do not know about where/how this needs to be done,
> >>>> but can do this if a dev outlines the process.
> >>>
> >>> Write trivial g729_parser which splits input into 8 byte packets.
> >>
> >> Thanks, I have implemented the 8 byte case.
> >>
> >>>
> >>> Problem is how to tell parser from demuxer that another non 8 byte
> >>> mode is in operation.
> >>> Because decoder operates in one of two modes, either 8 byte or 10
byte.
> >>
> >> This is tricky. A dirty but simple solution would be to add a field to
> >> the priv_data of the avctx,
> >> i.e to G729Context to represent the format, and use that in the parser.
> >> I have not seen any other parser do this though.
> >>
> >> Note that the parser is quite limited in what it can see:
> >> the AVCodecParserContext can't contain this information as far as I can
> >> tell,
> >> so only AVCodecContext can.
> >> In this case I don't know how to do this without resorting to the
priv_data.
> >
> > At decoder level you can not guess it, neither at demuxer level and
> > AFAIK only wav does
> > put multiple frames into single packet. The only way is via option but
> > AFAIK you can not read decoder options from parser.
>
> I must be missing something, g729dec.c decode_frame does set packet_type
> to the appropriate mode based on avpkt->size.
> In fact, this is how currently the two modes (8k vs 6.4k) are
differentiated.
> Why can't this be used to set a flag in avctx->priv_data (barring the
ugliness)?

For example 80 is multiple of 8 and 10 you can't use that to guess mode.
>
> >
> >>
> >> Any suggestions?
> >>
> >>>
> >>>>
> >>>> Thanks,
> >>>> Ganesh
> >>>> _______________________________________________
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> >>>> ffmpeg-devel at ffmpeg.org
> >>>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >>>>
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> >>
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