[FFmpeg-devel] Flac encoder and MPEG4 ALS

Justin Ruggles justinruggles
Sun Mar 30 17:33:05 CEST 2008

Jai Menon wrote:
> On Sunday 30 March 2008 13:55:49 Kostya wrote:
>> On Sun, Mar 30, 2008 at 09:44:51AM -0400, Justin Ruggles wrote:
>>> Kostya wrote:
>> [...]
>>>> I've looked at it once. Seems the most features are for floating-point
>>>> mode, baseline decoder should be comparatively easy. Especially if you
>>>> are the person who writes encoder to it ;)
>>> It has 2 entropy coders, plus another for floating-point.  It has 2 ways
>>> of doing multi-channel.  There are also several prediction methods.  The
>>> spec does not specifically say what is "baseline" vs. extended, but it
>>> would be simple enough to break down the task.
>> IIRC, both entropy coders are VLC - classical Shannon-Fano scheme and
>> classical Golomb codes. Prediction is also standard LPC and RLS, the latter
>> is quite rare in codecs though (MLP, APE, TTA ?).
>  and iirc golomb rice codes are used only for the tail end residuals, those in 
> center are encoded using block gilbert-moore codes........but i may be wrong

It is a choice of using only rice codes or a combination of bgmc and
rice codes as you described.


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