[libav-devel] [PATCH] get_bits: remove A32 variant

[Måns Rullgård]

Felipe Contreras <felipe.contreras at gmail.com> writes:

> On Fri, Dec 16, 2011 at 10:22 PM, Mans Rullgard <mans at mansr.com> wrote:
>> The A32 bitstream reader variant is only used on ARMv5 and for
>> Prores due to the larger bit cache this decoder requires.
>>
>> In benchmarks on ARMv5 (Marvell Sheeva) with gcc 4.6, the only
>> statistically significant difference between ALT and A32 is
>> a 4% advantage for ALT in FLAC decoding.  There is thus no (longer)
>> any reason to keep the A32 reader from this point of view.
>>
>> This patch adds an option to the ALT reader increasing the bit
>> cache to 32 bits as required by the Prores decoder.  Benchmarking
>> shows no significant change in speed on Intel i7.  Again, the
>> A32 reader fails to justify its existence.
>>
>> Signed-off-by: Mans Rullgard <mans at mansr.com>
>
> Cool! I've often wondered what was the point of it.

It may have at some point been faster on some CPU with some compiler.
We do not know.

-- 
Måns Rullgård
mans at mansr.com