> 在 2023年10月17日，上午5:24，Mark Thompson <s...@jkqxz.net> 写道：
>
> On 16/10/2023 10:13, Evgeny Pavlov wrote:
>> This commit reduces the sleep time on Windows to improve AMF encoding
>> performance on low resolution input videos.
>> This fix is for Windows only, because sleep() function isn't
>> very accurate on Windows OS.
>> Fix for issue #10622
>> Signed-off-by: Evgeny Pavlov <lucenti...@gmail.com>
>> ---
>> libavcodec/amfenc.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>> diff --git a/libavcodec/amfenc.c b/libavcodec/amfenc.c
>> index 061859f85c..0c95465d6e 100644
>> --- a/libavcodec/amfenc.c
>> +++ b/libavcodec/amfenc.c
>> @@ -770,7 +770,11 @@ int ff_amf_receive_packet(AVCodecContext *avctx,
>> AVPacket *avpkt)
>> if (query_output_data_flag == 0) {
>> if (res_resubmit == AMF_INPUT_FULL || ctx->delayed_drain ||
>> (ctx->eof && res_query != AMF_EOF) || (ctx->hwsurfaces_in_queue >=
>> ctx->hwsurfaces_in_queue_max)) {
>> block_and_wait = 1;
>> +#ifdef _WIN32
>> + av_usleep(0); //Sleep() is not precise on Windows OS.
>> +#else
>> av_usleep(1000);
>> +#endif
>> }
>> }
>> } while (block_and_wait);
>
> Wasting lots of power by spinning on a CPU core does not seem like a good
> answer to this problem. (I mean, presumably that is why Windows isn't
> honouring your request for a short sleep, because it wants timers to have
> larger gaps to avoid wasting power.)
If av_usleep is implemented via Sleep like current case, sleep 0 means yield
current thread, so it’s not busy wait in normal case (but it can be busy wait).
av_usleep(500) may looks better and do the same job by depending 500/1000 = 0.
I agree use sleep without real async is like a bug.
>
> Why is there a sleep here at all, anyway? An API for hardware encoding
> should be providing a way for the caller to wait for an outstanding operation
> to complete.
>
> Thanks,
>
> - Mark
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