[FFmpeg-devel] [PATCH] Set correct frame_size for Speex decoding

Michael Niedermayer michaelni
Mon Aug 17 03:14:18 CEST 2009

On Sun, Aug 16, 2009 at 12:26:32PM -0400, Justin Ruggles wrote:
> Michael Niedermayer wrote:
> > On Sun, Aug 16, 2009 at 05:07:18PM +0200, Michael Niedermayer wrote:
> >> On Sat, Aug 15, 2009 at 07:55:46PM -0400, Justin Ruggles wrote:
> >>> Michael Niedermayer wrote:
> > [...]
> >>>>>> what exactly is the argument you have that speex should not be handled like
> >>>>>> every other codec?!
> >>>>>> split it in a parser, the muxer muxes ONLY a single speex packet per
> >>>>>> container packet. Any extension from that is low priority and "patch welcome"
> >>>>>> IMHO ...
> >>>>> The downside for Speex is the container overhead since individual frames
> >>>>> are very small.
> >>>> this is true for many (most?) speech codecs
> >>>>
> >>>> also if we write our own speex encoder, it will only return one frame at a
> >>>> time.
> >>> Why would it have to?  
> >> because the API requires it, both encoders and decoders have to implement the
> >> API, a video encoder also cannot return 5 frames in one packet.
> >> APIs can be changed but you arent arguing for a API change you argue for
> >> ignoring the API and just doing something else.
> >>
> >>
> >>> If the user sets frame_size before initialization
> >>> to a number of samples that is a multiple of a single frame, it could
> >>> return multiple speex frames at once, properly joined together and
> >>> padded at the end.  With libspeex this is very easy to do because the
> >>> functionality is built into the API.
> >>>
> >>> I understand the desire to keep what are called frames as separate
> >>> entities, but in the case of Speex I see it as more advantagous to allow
> >>> the user more control when encoding.  If frames are always split up,
> >>> this limits the users options for both stream copy *and* for encoding to
> >>>  just 1 frame per packet.
> >>>
> >>> If you're dead-set against this idea, then I will finish the parser that
> >>> splits packets in order to continue with my other Speex patches, but I
> >>> don't like how limiting it would be for the user.
> >> i am againt speex handling things different than other speech codecs
> >> based on arguments that apply to other speech codecs as well.
> > 
> >> Also iam against passing data between muxer and codec layers in a way
> >> that violates the API.
> > 
> > ffmpeg seperates muxer and codec layers, writing a demuxer & decoder
> > that depend on things beyond the API (frames per frame) is going to
> > break things. We had similar great code (passing structs in AVPacket.data
> > because it was convenient) that also didnt turn out to be that great
> > and required a complete rewrite ...
> > 
> > 
> > ive alraedy said nut doesnt allow multiple frames per packet, but its
> > not just nut, avi as well doesnt allow multiple frames per packet
> > for VBR and either way avi needs to have its headers set up properly,
> > not with fake frame size and such and flv as we alaredy know has a 
> > issue with >8 frames per frame. All that is just what we know of will
> > break if you implement your hack, what else will break is something we
> > only would learn after some time.
> > 
> > IMHO, demuxer->parser->splited frames [unless it is not possible to split]
> > if a muxer can store multiple frames it can merge several depending on its
> > abilities and user provided parameters, that merging could also be done
> > as a bitstream filter.
> > But just skiping the spliting and merging and hoping that every container
> > would allow anyting that any other container allowed is just not going to
> > work. And even more so as we already know of many combinations that would
> > noz work
> I do understand your point.  There is a subtle difference with speex
> though.  The process of merging of frames into groups of frames is
> something that is specified by the codec itself, not the container.  To
> the container, it would be as transparent as for an audio codec that
> allows different numbers of samples/duration for a frame.  Nut would
> support it just fine, as it does with FLAC with different numbers of
> samples per frame.  As for FLV, it would be the same as if it doesn't
> allow over a certain number of samples per frame before getting choppy
> and/or crashing.

hmmm, could you quote the part of the speex spec that supports your view?
and provide a link to that spec. (iam asking for a quote instead of just
url cuz of the ML archive ...)

> That said, I think a bitstream filter could work too, but I don't know
> how options are passed to it, if that is even possible.

see FIXME:
static int opt_bsf(const char *opt, const char *arg)
    AVBitStreamFilterContext *bsfc= av_bitstream_filter_init(arg); //FIXME split name and args for filter at '='


int a= av_bitstream_filter_filter(bsfc, avctx, NULL,
put parameters in there


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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