[FFmpeg-devel] [PATCH 2/2] avcodec/put_bits: Make bit buffers 64-bit

[Michael Niedermayer]

On Fri, Jul 17, 2020 at 09:41:20PM +0200, Steinar H. Gunderson wrote:
> Change BitBuf into uint64_t on all supported 64-bit platforms.
> This means we need to flush the buffer less often, which is a
> significant speed win. 32-bit platforms are unchanged.
> Output bitstream is the same.
> 
> All API constraints are kept in place, e.g., you still cannot put_bits()
> more than 31 bits at a time. This is so that codecs cannot accidentally
> become 64-bit-only or similar.
> 
> Benchmarking on transcoding to various formats shows consistently
> positive results:
> 
>   dnxhd                 25.60 fps ->  26.26 fps ( +2.6%)
>   dvvideo               24.88 fps ->  25.17 fps ( +1.2%)
>   ffv1                  14.32 fps ->  14.58 fps ( +1.8%)
>   huffyuv               58.75 fps ->  63.27 fps ( +7.7%)
>   jpegls                 6.22 fps ->   6.34 fps ( +1.8%)
>   mjpeg                 48.65 fps ->  49.01 fps ( +0.7%)
>   mpeg1video            76.41 fps ->  77.01 fps ( +0.8%)
>   mpeg2video            75.99 fps ->  77.43 fps ( +1.9%)
>   mpeg4                 80.66 fps ->  81.37 fps ( +0.9%)
>   prores                12.35 fps ->  12.88 fps ( +4.3%)
>   prores_ks             16.20 fps ->  16.80 fps ( +3.7%)
>   rv20                  62.80 fps ->  62.99 fps ( +0.3%)
>   utvideo               68.41 fps ->  76.32 fps (+11.6%)
> 
> Note that this includes video decoding and all other encoding work,
> such as DCTs. If you isolate the actual bit-writing routines, it is
> likely to be much more.
> 
> Benchmark details: Transcoding the first 30 seconds of Big Buck Bunny
> in 1080p, Haswell 2.1 GHz, GCC 8.3, generally quantizer locked to
> 5.0. (Exceptions: DNxHD needs fixed bitrate, and JPEG-LS is so slow
> that I only took the first 10 seconds, not 30.) All runs were done
> ten times and single-threaded, top and bottom two results discarded to
> get rid of outliers, arithmetic mean between the remaining six.
> ---
>  libavcodec/put_bits.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/libavcodec/put_bits.h b/libavcodec/put_bits.h
> index c6a8f3ac14..d09c998991 100644
> --- a/libavcodec/put_bits.h
> +++ b/libavcodec/put_bits.h
> @@ -32,9 +32,15 @@
>  #include "libavutil/intreadwrite.h"
>  #include "libavutil/avassert.h"
>  
> +#if ARCH_AARCH64 || ARCH_IA64 || ARCH_MIPS64 || ARCH_SPARC64 || ARCH_X86_64

this needs a #include "config.h" or something equivalent

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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