[FFmpeg-devel] MOD support for FFmpeg (My GSoC 2010 task starts tomorrow)

[Vitor Sessak]

On 05/28/2010 02:05 PM, Sebastian Vater wrote:
> Vitor Sessak a ?crit :
>>
>> I'm still undecided of what is best, AVMEDIA_TYPE_AUDIO +
>> SAMPLE_FMT_COMPOSER or AVMEDIA_TYPE_COMPOSER. But the argument for
>> AVMEDIA_TYPE_AUDIO of having audioconvert.c do the PCM conversion in a
>> way that is transparent for caller apps is appealing.
>
> Yes, since that also allows 24-bit audio output for soundcards
> supporting it, etc.
> Maybe we should summarize pros/cons of both approaches, so it's easier
> to finally decide what's best.
>
>>
>>> - a FIXME here's is how a user would choose the samplerate, maybe a
>>> AVCodecContext.request_sample_rate in the style of channel_mask?
>>
>> Maybe "-sampler_flags" in the same way we have "-sws_flags"?
>
> In my eyes, we won't need that for the output PCM stuff, just use
> avctx->bits_per_coded_sample, avctx->sample_rate, as we do for other
> sample formats, too. Only the internal mixing engine has to be a bit
> more configurable.
>
>>
>>
>> Yes, I'd say that a very important piece of code would be the data
>> structures holding the decoded collection of notes, instruments, etc.
>> This will be what the decoders will output (and what we mean by
>> SAMPLE_FMT_COMPOSER). Since this should be able to describe all
>> supported MOD formats, it should be pretty flexible. I think it should
>> be part of libavcodec. Also, the caller app might want to known which
>> instruments are being played and when and how, so this structs should
>> be part of the public API (which implies tough review). IMHO, this
>> should be the first thing to be reviewed and committed, since it
>> blocks all the rest.
>
> I actually plan to start with porting the TuComposer header files (the
> mod structure itself), then move on to mixing engine stuff (which more
> "interferes" with lavc/lavf). My idea as discussed on IRC was like this:
> tucomposer/tucomposer.h =>  libavsequencer/avseq.h
> tucomposer/player.h, tucomposer/external/mixer.h =>  libavsequencer/player.h
> tucomposer/module.h, song.h, position.h, track.h, instr.h, sample.h,
> synth.h =>  libavsequencer/module.h

Huh? Nothing in libavcodec?

-Vitor