flac dev - Sep 2004 - Re: process for petitioning for more flac hardware support

> 
> i was wondering how one would go about approaching hardware
> manufacturers to support flac.
> 
One thing to do first might be to make sure that flac is suitable to
run on lost cost hardware. For example the amount of buffering required
in the decoder.

If I understand the flac format correctly, all decoders must support
block sizes upto 65535 samples (ie 256k of decoded stereo data).

For comparison, a SW MP3 decoder running on an embedded cpu can be run
in as little as 32k bytes of RAM (which includes 9k required to double
buffer _two_ frames (1152 samples each) of decoded audio).

Maybe it is always possible to play audio from a flac block without
buffering and decoding the whole block first (I don't know - I haven't
studied the source) but some information covering this type of issue on
the flac website might be a good starting point for persuading HW
manufacturers.

Just my 2 cents.... :-)

Andre
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--- Andre <armcc@lycos.com> wrote:
> > 
> > i was wondering how one would go about approaching hardware
> > manufacturers to support flac.
> > 
> 
> One thing to do first might be to make sure that flac is suitable to
> run on lost cost hardware. For example the amount of buffering
> required
> in the decoder.
> 
> If I understand the flac format correctly, all decoders must support
> block sizes upto 65535 samples (ie 256k of decoded stereo data).
FLAC specifies a subset of the whole format that make it
more amenable to small hardware implementations.  The command-
line encoder currently generates subset files, with a max
block size of 4308 samples unless you explicitly give it a
different number.  So while it's possible to have 64k samples
in a block, you have to force a large blocksize when encoding,
then knowingly tell the encoder via another call
(FLAC__stream_encoder_set_streamable_subset(encoder, false))
which is what 'flac --lax' does, that you are straying from the
subset.

There are warnings in the docs about the consequences of
--lax but maybe it's not clear enough.
> Maybe it is always possible to play audio from a flac block without
> buffering and decoding the whole block first (I don't know - I
> haven't
> studied the source) but some information covering this type of issue
> on
> the flac website might be a good starting point for persuading HW
> manufacturers.
This is possible as long as you don't care about checking the
data against the CRC before playback.

Josh


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