[FFmpeg-devel] [PATCH, v2] avcodec/amfenc: increase precision of Sleep() on Windows
Cameron Gutman
aicommander at gmail.com
Wed Aug 21 10:01:31 EEST 2024
On Mon, Aug 19, 2024 at 9:31 AM Araz Iusubov <primeadvice at gmail.com> wrote:
>
> From: Evgeny Pavlov <lucenticus at gmail.com>
>
> This commit increase precision of Sleep() function on Windows.
> This fix reduces the sleep time on Windows to improve AMF encoding
> performance on low resolution input videos.
>
> Fix for issue #10622
>
> We evaluated CreateWaitableTimerExW with
> CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag. In fact, this function has
> the same precision level as the Sleep() function.
>
The proper way to get a wait that completes under the tick period
on Windows is to use a waitable object, such as an event. Polling
for AMF output like we do now wastes power and increases latency.
I see that AMF has a QUERY_TIMEOUT option available to determine
how long QueryOutput() blocks waiting for output to be available.
Does this option do a something sane internally like waiting on
an event or is just doing the same polling that we already do?
> Usually changing the time resolution will only affect the current
> process and will not impact other processes, thus it will not cause a
> global effect on the current system. Here is an info from
> documentation on timeBeginPeriod
> https://learn.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timebeginperiod
>
> "Prior to Windows 10, version 2004, this function affects a global
> Windows setting. For all processes Windows uses the lowest value (that
> is, highest resolution) requested by any process. Starting with
> Windows 10, version 2004, this function no longer affects global timer
> resolution. For processes which call this function, Windows uses the
> lowest value (that is, highest resolution) requested by any process.
> For processes which have not called this function, Windows does not
> guarantee a higher resolution than the default system resolution."
>
> We provide the following measurement to show performance improvements
> with this patch.
>
> 1. Performance tests show that this high precision sleep will improve
> performance, especially for low resolution sequences, it can get about
> 20% improvement.
>
> Frames Per Second (FPS) being encoded by the hardware encoder (Navi 31
> RX7900XT ):
>
> Source Type: H.264 , Output Type: H.264
> (Sorry for bad formatting)
> No. | Sequence Resolution | No. of Frames| FPS Before patch |
> FPS after patch | Difference | Improvement %
> ----|-----------------------|--------------|------------------------|-------------------|---------------|----------
> 1 | 480x360 | 8290 | 2030 |
> 2365 | 335 | 16.5%
> 2 | 720x576 | 8290 | 1440 |
> 1790 | 350 | 24.3%
> 3 | 1280x720 | 8290 | 1120 |
> 1190 | 70 | 6.3%
> 4 | 1920x1080 | 8290 | 692 |
> 714 | 22 | 3.2%
> 5 | 3840x2160 | 8290 | 200 |
> 200 | 0 | 0.0%
>
> The sample ffmpeg command line:
> $ ffmpeg.exe -y -hwaccel d3d11va -hwaccel_output_format d3d11 -i
> input.mp4 -c:v h264_amf out.mp4
> where input.mp4 should be changed to corresponding resolution input
> H.264 format bitstream.
>
> 2. The power tests show an increase in power is within limit scope.
>
> The purpose of the power test is to examine the increase in CPU power
> consumption due to the improvement in CPU time resolution after using
> this patch. We were testing a product from AMD called Phoenix, which
> we refer to as an APU. It combines a general-purpose AMD CPU and a 3D
> integrated graphics processing unit (IGPU) on a single die. Only the
> APU has a DAP connector to the board's power rails.
>
> We got the power test data shown below:
>
> | | 480x360 | 720x576 | 1280x720 |
> 1920x1080 | 3840x2160 | average
> |------------------------|-----------|------------|----------|-----------|-----------|--------
> |CPU power change | 1.93% | 2.43% | -1.69% | 3.49%
> | 2.92% | 1.82%
> |APU power total change | 0.86% | 1.34% | -0.62% | 1.54%
> | -0.58% | 0.51
>
> When using a high precision clock by applying the patch, the average
> power consumption for CPU increases 1.82%, and the APU total increases
> 0.51%. We can see the power increase in power not very significant.
>
> Signed-off-by: Evgeny Pavlov <lucenticus at gmail.com>
> ---
> libavcodec/amfenc.c | 31 +++++++++++++++++++++++++++++++
> libavcodec/amfenc.h | 3 +++
> 2 files changed, 34 insertions(+)
>
> diff --git a/libavcodec/amfenc.c b/libavcodec/amfenc.c
> index 061859f85c..55e24856e8 100644
> --- a/libavcodec/amfenc.c
> +++ b/libavcodec/amfenc.c
> @@ -42,7 +42,12 @@
> #endif
>
> #ifdef _WIN32
> +#include <timeapi.h>
> #include "compat/w32dlfcn.h"
> +
> +typedef MMRESULT (*timeapi_fun)(UINT uPeriod);
> +#define WINMM_DLL "winmm.dll"
> +
> #else
> #include <dlfcn.h>
> #endif
> @@ -113,6 +118,9 @@ static int amf_load_library(AVCodecContext *avctx)
> AMFInit_Fn init_fun;
> AMFQueryVersion_Fn version_fun;
> AMF_RESULT res;
> +#ifdef _WIN32
> + timeapi_fun time_begin_fun;
> +#endif
>
> ctx->delayed_frame = av_frame_alloc();
> if (!ctx->delayed_frame) {
> @@ -145,6 +153,16 @@ static int amf_load_library(AVCodecContext *avctx)
> AMF_RETURN_IF_FALSE(ctx, res == AMF_OK, AVERROR_UNKNOWN, "GetTrace() failed with error %d\n", res);
> res = ctx->factory->pVtbl->GetDebug(ctx->factory, &ctx->debug);
> AMF_RETURN_IF_FALSE(ctx, res == AMF_OK, AVERROR_UNKNOWN, "GetDebug() failed with error %d\n", res);
> +
> +#ifdef _WIN32
> + // Increase precision of Sleep() function on Windows platform
> + ctx->winmm_lib = dlopen(WINMM_DLL, RTLD_NOW | RTLD_LOCAL);
> + AMF_RETURN_IF_FALSE(ctx, ctx->winmm_lib != NULL, 0, "DLL %s failed to open\n", WINMM_DLL);
> + time_begin_fun = (timeapi_fun)dlsym(ctx->winmm_lib, "timeBeginPeriod");
> + AMF_RETURN_IF_FALSE(ctx, time_begin_fun != NULL, 0, "DLL %s failed to find function %s\n", WINMM_DLL, "timeBeginPeriod");
> + time_begin_fun(1);
> +#endif //_WIN32
> +
> return 0;
> }
>
> @@ -375,6 +393,9 @@ static int amf_init_encoder(AVCodecContext *avctx)
> int av_cold ff_amf_encode_close(AVCodecContext *avctx)
> {
> AmfContext *ctx = avctx->priv_data;
> +#ifdef _WIN32
> + timeapi_fun time_end_fun;
> +#endif //_WIN32
>
> if (ctx->delayed_surface) {
> ctx->delayed_surface->pVtbl->Release(ctx->delayed_surface);
> @@ -410,6 +431,16 @@ int av_cold ff_amf_encode_close(AVCodecContext *avctx)
> av_frame_free(&ctx->delayed_frame);
> av_fifo_freep2(&ctx->timestamp_list);
>
> +#ifdef _WIN32
> + if (ctx->winmm_lib) {
> + time_end_fun = (timeapi_fun)dlsym(ctx->winmm_lib, "timeEndPeriod");
> + AMF_RETURN_IF_FALSE(ctx, time_end_fun != NULL, 0, "DLL %s failed to find function %s\n", WINMM_DLL, "timeEndPeriod");
> + time_end_fun(1);
> + dlclose(ctx->winmm_lib);
> + ctx->winmm_lib = NULL;
> + }
> +#endif //_WIN32
> +
> return 0;
> }
>
> diff --git a/libavcodec/amfenc.h b/libavcodec/amfenc.h
> index 2dbd378ef8..35bcf1dfe3 100644
> --- a/libavcodec/amfenc.h
> +++ b/libavcodec/amfenc.h
> @@ -50,6 +50,9 @@ typedef struct AmfContext {
> AVClass *avclass;
> // access to AMF runtime
> amf_handle library; ///< handle to DLL library
> +#ifdef _WIN32
> + amf_handle winmm_lib; ///< handle to winmm DLL library
> +#endif //_WIN32
> AMFFactory *factory; ///< pointer to AMF factory
> AMFDebug *debug; ///< pointer to AMF debug interface
> AMFTrace *trace; ///< pointer to AMF trace interface
> --
> 2.45.2.windows.1
>
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