[FFmpeg-devel] ALS optimizations

Guennadi Liakhovetski g.liakhovetski
Fri Dec 17 08:25:50 CET 2010

Hi Justin

On Thu, 16 Dec 2010, Justin Ruggles wrote:

> On 12/16/2010 08:56 AM, Guennadi Liakhovetski wrote:
> > I'm trying to optimize ALS decoding for a specific platform. There are 
> > several repeated MUL64() calls in libavcodec/alsdec.c, that can be very 
> > well optimized. one of them already provided a 10% boost. But others lie 
> > on paths, that are never entered with sample ALS files from "fate." How 
> > can I produce or where can I get from files, that would also use those 
> > other paths?
> > 
> > E.g., in decode_var_block_data() "if (*bd->use_ltp)" is never entered, 
> > similarly "if (bd->ra_block)" and revert_channel_correlation() is never 
> > called at all.
> The files in FATE do not cover all features of ALS (there are many
> features).  There are more reference files available from ISO or you can
> create your own that use various features using the reference encoder.

I have been also pointed out to the reference software from TU-Berlin, 
which I've downloaded and used to create a couple of files, which a recent 
ffmpeg couldn't decode - even without any options. As for available ISO 
files - couldn't find any, are they not only for members / for a fee? 
Would you happen to have a link at hand?

Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer

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