[FFmpeg-devel] [PATCH 1/3] ffmpeg: allocate the output hwaccel AVFrame only once

[James Almer]

On 11/18/2021 5:35 AM, Andreas Rheinhardt wrote:
> James Almer:
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>   fftools/ffmpeg.c    |  3 +++
>>   fftools/ffmpeg.h    |  1 +
>>   fftools/ffmpeg_hw.c | 17 ++++++-----------
>>   3 files changed, 10 insertions(+), 11 deletions(-)
>>
>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>> index d141f34df9..26030ed25e 100644
>> --- a/fftools/ffmpeg.c
>> +++ b/fftools/ffmpeg.c
>> @@ -640,6 +640,7 @@ static void ffmpeg_cleanup(int ret)
>>           av_frame_free(&ist->sub2video.frame);
>>           av_freep(&ist->filters);
>>           av_freep(&ist->hwaccel_device);
>> +        av_frame_free(&ist->hwaccel_frame);
>>           av_freep(&ist->dts_buffer);
>>   
>>           avcodec_free_context(&ist->dec_ctx);
>> @@ -2412,6 +2413,8 @@ static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output, int64_
>>           return AVERROR(ENOMEM);
>>       if (!ist->filter_frame && !(ist->filter_frame = av_frame_alloc()))
>>           return AVERROR(ENOMEM);
>> +    if (!ist->hwaccel_frame && !(ist->hwaccel_frame = av_frame_alloc()))
>> +        return AVERROR(ENOMEM);
>>       decoded_frame = ist->decoded_frame;
>>       if (ist->dts != AV_NOPTS_VALUE)
>>           dts = av_rescale_q(ist->dts, AV_TIME_BASE_Q, ist->st->time_base);
>> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
>> index 30225e9ffe..17135cb830 100644
>> --- a/fftools/ffmpeg.h
>> +++ b/fftools/ffmpeg.h
>> @@ -382,6 +382,7 @@ typedef struct InputStream {
>>       enum AVPixelFormat hwaccel_pix_fmt;
>>       enum AVPixelFormat hwaccel_retrieved_pix_fmt;
>>       AVBufferRef *hw_frames_ctx;
>> +    AVFrame *hwaccel_frame;
>>   
>>       /* stats */
>>       // combined size of all the packets read
>> diff --git a/fftools/ffmpeg_hw.c b/fftools/ffmpeg_hw.c
>> index 14e702bd92..d5034d4f6a 100644
>> --- a/fftools/ffmpeg_hw.c
>> +++ b/fftools/ffmpeg_hw.c
>> @@ -18,6 +18,7 @@
>>   
>>   #include <string.h>
>>   
>> +#include "libavutil/avassert.h"
>>   #include "libavutil/avstring.h"
>>   #include "libavutil/pixdesc.h"
>>   #include "libavfilter/buffersink.h"
>> @@ -500,7 +501,7 @@ int hw_device_setup_for_encode(OutputStream *ost)
>>   static int hwaccel_retrieve_data(AVCodecContext *avctx, AVFrame *input)
>>   {
>>       InputStream *ist = avctx->opaque;
>> -    AVFrame *output = NULL;
>> +    AVFrame *output = ist->hwaccel_frame;
>>       enum AVPixelFormat output_format = ist->hwaccel_output_format;
>>       int err;
>>   
>> @@ -509,9 +510,8 @@ static int hwaccel_retrieve_data(AVCodecContext *avctx, AVFrame *input)
>>           return 0;
>>       }
>>   
>> -    output = av_frame_alloc();
>> -    if (!output)
>> -        return AVERROR(ENOMEM);
>> +    av_assert0(output);
>> +    av_frame_unref(output);
> 
> If you move the allocation of the frame here, you can avoid the
> allocation in case no hwaccel as well as the assert.
> The av_frame_unref() above is btw unnecessary.

Here where? You mean in hw_device_setup_for_encode() above?

> 
>>   
>>       output->format = output_format;
>>   
>> @@ -519,24 +519,19 @@ static int hwaccel_retrieve_data(AVCodecContext *avctx, AVFrame *input)
>>       if (err < 0) {
>>           av_log(avctx, AV_LOG_ERROR, "Failed to transfer data to "
>>                  "output frame: %d.\n", err);
>> -        goto fail;
>> +        return err;
>>       }
>>   
>>       err = av_frame_copy_props(output, input);
>>       if (err < 0) {
>>           av_frame_unref(output);
>> -        goto fail;
>> +        return err;
>>       }
>>   
>>       av_frame_unref(input);
>>       av_frame_move_ref(input, output);
>> -    av_frame_free(&output);
> 
> I wonder whether we should support src == dst in
> av_hwframe_transfer_data() (potentially with a flag). This would make
> this function and the implicit copying of side-data superfluous.
> (av_hwframe_transfer_data() itself could btw. make use of the fact that
> it lives in libavutil and avoid allocating an AVFrame).
> 
>>   
>>       return 0;
>> -
>> -fail:
>> -    av_frame_free(&output);
>> -    return err;
>>   }
>>   
>>   int hwaccel_decode_init(AVCodecContext *avctx)
>>
> 
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