Re: [FFmpeg-devel] [PATCH 2/3] lavc: replace ff_thread_get_buffer() with ff_get_buffer()

From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 2/3] lavc: replace ff_thread_get_buffer() with ff_get_buffer()
Date: Fri, 8 Mar 2024 11:19:59 +0100
Message-ID: <GV1SPRMB0052C6557FA6BFB2F0A5CFDD8F272@GV1SPRMB0052.EURP250.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <170989285192.7287.17016576053815588581@lain.khirnov.net>

Anton Khirnov:
> Quoting Andreas Rheinhardt (2024-03-08 11:03:18)
>> Anton Khirnov:
>>> ff_thread_get_buffer() has exactly the same semantics as
>>> ff_get_buffer(), except it is supposed to be used in frame-threaded
>>> decoders. Since the decoder instance knows whether frame threading is in
>>> use, there is no point in forcing decoder implementations to use a
>>> different function merely because they happen to support frame
>>> threading.
>>> ---
>>>  libavcodec/aic.c              |  4 ++--
>>>  libavcodec/alac.c             |  4 ++--
>>>  libavcodec/av1dec.c           |  2 +-
>>>  libavcodec/avcodec_internal.h | 13 +++++++++++++
>>>  libavcodec/bitpacked_dec.c    |  4 ++--
>>>  libavcodec/cfhd.c             |  4 ++--
>>>  libavcodec/cllc.c             |  8 ++++----
>>>  libavcodec/cri.c              |  2 +-
>>>  libavcodec/decode.c           | 13 ++++++++++++-
>>>  libavcodec/dnxhddec.c         |  2 +-
>>>  libavcodec/dvdec.c            |  2 +-
>>>  libavcodec/dxtory.c           | 12 ++++++------
>>>  libavcodec/dxv.c              |  4 ++--
>>>  libavcodec/exr.c              |  2 +-
>>>  libavcodec/flacdec.c          |  4 ++--
>>>  libavcodec/fraps.c            |  4 ++--
>>>  libavcodec/h264_slice.c       |  2 +-
>>>  libavcodec/hapdec.c           |  4 ++--
>>>  libavcodec/hdrdec.c           |  2 +-
>>>  libavcodec/hevcdec.c          |  2 +-
>>>  libavcodec/hqx.c              |  4 ++--
>>>  libavcodec/huffyuvdec.c       |  4 ++--
>>>  libavcodec/jpeg2000dec.c      |  2 +-
>>>  libavcodec/lagarith.c         | 12 ++++++------
>>>  libavcodec/lcldec.c           |  4 ++--
>>>  libavcodec/magicyuv.c         |  2 +-
>>>  libavcodec/mdec.c             |  4 ++--
>>>  libavcodec/notchlc.c          |  2 +-
>>>  libavcodec/photocd.c          |  2 +-
>>>  libavcodec/pixlet.c           |  2 +-
>>>  libavcodec/pngdec.c           |  4 ++--
>>>  libavcodec/proresdec2.c       |  2 +-
>>>  libavcodec/pthread_frame.c    |  7 ++-----
>>>  libavcodec/qoidec.c           |  2 +-
>>>  libavcodec/rtv1.c             |  2 +-
>>>  libavcodec/sheervideo.c       |  4 ++--
>>>  libavcodec/takdec.c           |  5 +++--
>>>  libavcodec/thread.h           | 10 ----------
>>>  libavcodec/tiff.c             |  2 +-
>>>  libavcodec/tta.c              |  4 ++--
>>>  libavcodec/utils.c            |  5 -----
>>>  libavcodec/utvideodec.c       |  4 ++--
>>>  libavcodec/v210dec.c          |  4 ++--
>>>  libavcodec/v410dec.c          |  4 ++--
>>>  libavcodec/vaapi_av1.c        |  4 ++--
>>>  libavcodec/vble.c             |  4 ++--
>>>  libavcodec/vmixdec.c          |  2 +-
>>>  libavcodec/vvc/vvc_refs.c     |  4 ++--
>>>  libavcodec/wbmpdec.c          |  2 +-
>>>  libavcodec/webp.c             |  2 +-
>>>  libavcodec/ylc.c              |  4 ++--
>>>  51 files changed, 110 insertions(+), 103 deletions(-)
>>>
>>
>> -1: This adds avoidable runtime checks.
> 
> What checks and why is that a problem?
> 
It adds a runtime check to every call to ff_get_buffer() by every
decoder not supporting frame-threading (by checking whether
frame-threading is currently in use).
Every avoidable runtime check should always be avoided.

- Andreas

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