[FFmpeg-devel] [PATCH] ALS decoder
Sun Aug 23 13:41:22 CEST 2009
Thilo Borgmann wrote:
>> i see, still at least the declarations could be moved in the loop
>> and f course if something can be done about the 64bit that would be great
>> speedwise ...
> Unfortunately, the reference decoder also uses 64-bit for them.
The specification indicates 64-bit as well. I'm not sure if it is
possible, but if you can somehow get bit-exact results using 32-bit then
>>>>>> + if (sconf->resolution == 2 || sconf->floating)
>>>>>> + const_val_bits = 24;
>>>>>> + else
>>>>>> + const_val_bits = avctx->bits_per_raw_sample;
>>>>> why would const_val_bits != avctx->bits_per_raw_sample ?
>>>> bits_per_raw_sample = 32 for floating sconf->floating.
>>> To explain this further... The way floating-point in ALS works is that
>>> it has a 24-bit integer part and a floating-point difference part. So
>>> the final output is 32-bit, even though the integer part decoded here is
>>> only 24-bit.
>> the sconf->resolution == 2 still is useless?
> The output format in that case is also set to SAMPLE_FMT_S32.
Even though the output sample format is S32, bits_per_raw_sample should
still reflect the source bit depth, I think.
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