[Libav-user] QTKit -> Libav: has it ever been done?

Paul B Mahol onemda at gmail.com
Wed Mar 27 13:19:40 CET 2013

On 3/27/13, Brad O'Hearne <brado at bighillsoftware.com> wrote:
> In lieu of having no luck over several weeks getting video + audio samples
> captured from QTKit resampled and encoded with Libav to FLV (with video),
> I've kind of hit a bit of a brick wall. The runnable Mac app and source
> demonstrating this use case hasn't apparently shed any light on why the
> audio being encoded is junk. While my gut all along has been that there's
> something relatively simple at work, perhaps a pointer problem or something,
> at the same time I've been over this fairly modest section of code so many
> times I'm not sure what more to try.
> Again, my use case:
> QTKit capture (audio / video) -> convert (video)/resample (audio) -> encode
> to FLV -> output (file or network stream)
> Up to this point, I've assumed all of the problem was in my code. I still
> don't doubt that is likely the case, but given no headway looking for the
> problem there, or to whatever degree anyone else has taken a look at the
> sample app I provided it also hasn't rendered any real headway, I started
> looking in other media libraries which either depend or appear to partially
> depend on Libav. Basically what appears to be the case is that they don't
> use Libav on the other side of QTKit capture, so as of now, I am not aware
> of any example which is publicly available demonstrating that this has been
> done.
> So at this point, it seems a decent question to consider if maybe the
> problem lies in Libav. I think there's a pretty simple question to ask: has
> a QTSampleBuffer ever been used to fill a sample array, resampled, and
> encoded to FLV? -- i.e. does anyone actually know if this works? If so, I
> would be much obliged if you could direct me to the unit test or code
> example which demonstrates this, and I should be able to figure out what
> deficiency exists in my code. If such a unit test or code example does *not*
> exist, then I guess a question for the maintainers -- what do you think the
> chances are that there's a bug somewhere in either resampling or the
> adpcm_swf codec that could be affecting audio?
> Thanks, I greatly appreciate it.

Provide raw output given by QTKit whatever, and I'm sure someone will
give you solution for your problem.

> Brad
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