[FFmpeg-devel] [PATCH] fix speex sample

Michael Niedermayer michaelni
Thu Apr 9 21:37:31 CEST 2009

On Thu, Apr 09, 2009 at 10:24:27AM -0700, Baptiste Coudurier wrote:
> On 4/9/2009 7:06 AM, Michael Niedermayer wrote:
> > On Thu, Apr 09, 2009 at 09:39:24AM +0200, Diego Biurrun wrote:
> >> On Thu, Apr 09, 2009 at 04:46:34AM +0200, Michael Niedermayer wrote:
> >>> On Wed, Apr 08, 2009 at 06:30:56PM -0700, Baptiste Coudurier wrote:
> >>>> Michael Niedermayer wrote:
> >>>>> On Wed, Apr 08, 2009 at 05:26:11PM -0700, Baptiste Coudurier wrote:
> >>>>>> On 4/8/2009 5:02 PM, Michael Niedermayer wrote:
> >>>>>>> On Wed, Apr 08, 2009 at 04:21:32PM -0700, Baptiste Coudurier wrote:
> >>>>>>>> Mpeg2 decoder has an important bug IMHO since some time. I
> >>>>>>>> reported it, and libmpeg2 does not have this bug and decodes
> >>>>>>>> correctly the first 2 frames. I lack some knowledge of the
> >>>>>>>> surrounding code, but I tried to work on it at least. It should
> >>>>>>>> not take you much time to figure out the problem I guess.
> >>>>>>> thats a feature request not a bug, its something very well known
> >>>>>>> since the code was written.
> >>>>>> What was your argument about other implementation supporting it ? 
> >>>>>> Oh yes, users will stop using yours to use the one supporting it.
> >>>>>>
> >>>>>> FYI, many of my samples use this mechanism, I just didn't really
> >>>>>> realize it, I thought it was just broken link but finally, I
> >>>>>> discovered that libavcodec deliberately _skip_ 2 frames, even
> >>>>>> without telling you !
> >>>>>>
> >>>>>> Solution is simple, until fixed I will use libmpeg2.
> >>>>> poor libmpeg2
> >>>> I'd say poor libavcodec, loosing one heavy user because of lousy
> >>>> maintainership.
> >>> not implementing all feature requests != lousy maintainership
> >>> if you want this feature, you can implement it.
> >> So I will rephrase the question: What will it take for you to implement
> >> this so that FFmpeg can be a complete libmpeg2 replacement?
> > 
> > I honestly have no interrest in implementing this. This is not a feature
> > that should affect any ones decission of which decoder to use.
> I'm not sure but loosing these 2 frames is really annoying for me, I
> basically loose frame accuracy.

i dont see how, its a gamble if you will get 0, 1, 2 or even 99 frames prior
of the keyframe if this feature request is implemented. And that is for
each seek, not per file.
how that improves accuracy relative to not receiving frames prior to
the timestamp to which you seek, i dont understand.

> > Also if someone considers this feature to be so critical to him, he
> > can implement it, its simple "patch welcome"
> Well, I'm not disagreeing here, I tried to fix it myself and submitted a
> patch. I'm not sure to understand everything though.
> Like I don't clearly understand why closed_gop and broken_link would
> matter if we get error-concealment in this case.
> Like you said these flags might be wrongly set.

am i the only one that thinks that duplicating frames randomly through
error concealment on every seek is a poor idea?

> Do you mean that If broken_link is set, then these 2 frames cannot be
> decoded and should be discarded ?

no closed_gop must be set to 1 for the frames to be decodeable


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Rewriting code that is poorly written but fully understood is good.
Rewriting code that one doesnt understand is a sign that one is less smart
then the original author, trying to rewrite it will not make it better.
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