[FFmpeg-devel] [PATCH] MLP Encoder

Ramiro Polla ramiro.polla
Fri Aug 15 17:57:39 CEST 2008


On Thu, Aug 14, 2008 at 5:16 AM, Ian Caulfield <ian.caulfield at gmail.com> wrote:
> 2008/8/14 Ramiro Polla <ramiro.polla at gmail.com>:
>> Hello,
>> Attached is the MLP encoder written as part of the Google Summer of
>> Code project and mentored by Justin Ruggles.
>> Things that are not quite complete:
>> - The filters... The filtering code is there and it works, but finding
>> good coefficients is not. The FIR code from flacenc.c can be plugged
>> in there quite easily, but it takes more bits to encode the
>> coefficients than the raw data. It might be because of the small frame
>> size (40 samples @ 44100kHz). If the frame size was raised to
>> something like 256 samples, the compression would be much better, but
>> the RE work shows that the bitstream doesn't allow this. Also my
>> attempts with IIR filters weren't successful.
> You shouldn't need to supply coefficients very often - once every
> major sync ought to be enough...

I imagine for best compression I could buffer up frames and run the
filter in the first frame, then first + second, on and on, until the
filter no longer provides a good approximation, then encode the
packets up to that point and return them. Is this a good idea, and if
it is, what's the best way to buffer the frames in a way that doesn't
mess up sync?

Ramiro Polla

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