[FFmpeg-devel] [PATCH 13/14] mmal: add option copy_frame to support retrieving sw frames w/o copy

[wm4]

On Sat, 16 Dec 2017 13:48:05 +0800
Wang Bin <wbsecg1 at gmail.com> wrote:

> 2017-12-16 2:50 GMT+08:00 wm4 <nfxjfg at googlemail.com>:
> > On Fri, 15 Dec 2017 15:05:50 +0800
> > wbsecg1 at gmail.com wrote:
> >  
> >> From: wang-bin <wbsecg1 at gmail.com>
> >>
> >> mmal buffer->data is already in host memory. AFAIK decoders implemented in omx must
> >> be configured to output frames to either memory or something directly used by renderer,
> >> for example mediacodec surface, mmal buffer and omxil eglimage.
> >> test result: big buck bunny 1080p fps increases from about 100 to 110 if copy_frame is
> >> turned off
> >> ---
> >>  libavcodec/mmaldec.c | 31 +++++++++++++++++++++++--------
> >>  1 file changed, 23 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/libavcodec/mmaldec.c b/libavcodec/mmaldec.c
> >> index c1cfb09283..9cd6c6558f 100644
> >> --- a/libavcodec/mmaldec.c
> >> +++ b/libavcodec/mmaldec.c
> >> @@ -69,6 +69,7 @@ typedef struct MMALDecodeContext {
> >>      AVClass *av_class;
> >>      int extra_buffers;
> >>      int extra_decoder_buffers;
> >> +    int copy_frame;
> >>
> >>      MMAL_COMPONENT_T *decoder;
> >>      MMAL_QUEUE_T *queue_decoded_frames;
> >> @@ -139,7 +140,6 @@ static int ffmmal_set_ref(AVFrame *frame, FFPoolRef *pool,
> >>      atomic_fetch_add_explicit(&ref->pool->refcount, 1, memory_order_relaxed);
> >>      mmal_buffer_header_acquire(buffer);
> >>
> >> -    frame->format = AV_PIX_FMT_MMAL;
> >>      frame->data[3] = (uint8_t *)ref->buffer;
> >>      return 0;
> >>  }
> >> @@ -650,20 +650,34 @@ static int ffmal_copy_frame(AVCodecContext *avctx,  AVFrame *frame,
> >>
> >>          if ((ret = ffmmal_set_ref(frame, ctx->pool_out, buffer)) < 0)
> >>              goto done;
> >> +        frame->format = AV_PIX_FMT_MMAL;
> >>      } else {
> >>          int w = FFALIGN(avctx->width, 32);
> >>          int h = FFALIGN(avctx->height, 16);
> >>          uint8_t *src[4];
> >>          int linesize[4];
> >>
> >> -        if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
> >> -            goto done;
> >> +        if (ctx->copy_frame) {
> >> +            if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
> >> +                goto done;
> >>
> >> -        av_image_fill_arrays(src, linesize,
> >> -                             buffer->data + buffer->type->video.offset[0],
> >> -                             avctx->pix_fmt, w, h, 1);
> >> -        av_image_copy(frame->data, frame->linesize, src, linesize,
> >> -                      avctx->pix_fmt, avctx->width, avctx->height);
> >> +            av_image_fill_arrays(src, linesize,
> >> +                                buffer->data + buffer->type->video.offset[0],
> >> +                                avctx->pix_fmt, w, h, 1);
> >> +            av_image_copy(frame->data, frame->linesize, src, linesize,
> >> +                        avctx->pix_fmt, avctx->width, avctx->height);
> >> +        } else {
> >> +            if ((ret = ff_decode_frame_props(avctx, frame)) < 0)
> >> +                goto done;
> >> +            /* buffer->type->video.offset/pitch[i]; is always 0 */
> >> +            av_image_fill_arrays(src, linesize,
> >> +                                buffer->data + buffer->type->video.offset[0],
> >> +                                avctx->pix_fmt, w, h, 1);
> >> +            if ((ret = ffmmal_set_ref(frame, ctx->pool_out, buffer)) < 0)
> >> +                goto done;
> >> +            memcpy(frame->data, src, sizeof(src));
> >> +            memcpy(frame->linesize, linesize, sizeof(linesize));
> >> +        }
> >>      }
> >>
> >>      frame->pts = buffer->pts == MMAL_TIME_UNKNOWN ? AV_NOPTS_VALUE : buffer->pts;
> >> @@ -842,6 +856,7 @@ AVHWAccel ff_wmv3_mmal_hwaccel = {
> >>  static const AVOption options[]={
> >>      {"extra_buffers", "extra buffers", offsetof(MMALDecodeContext, extra_buffers), AV_OPT_TYPE_INT, {.i64 = 10}, 0, 256, 0},
> >>      {"extra_decoder_buffers", "extra MMAL internal buffered frames", offsetof(MMALDecodeContext, extra_decoder_buffers), AV_OPT_TYPE_INT, {.i64 = 10}, 0, 256, 0},
> >> +    {"copy_frame", "copy deocded data to avframe", offsetof(MMALDecodeContext, copy_frame), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 256, 0},
> >>      {NULL}
> >>  };
> >>  
> >
> > Didn't check too closely what exactly the patch does, but adding an
> > option for it sounds very wrong. The user select in the get_format
> > callback whether a GPU surface is output (MMAL pixfmt), or software.  
> 
> Avoid copying data from mmal buffer->data to avframe data. Instead,
> just fill strides and address of each plane in avframe, and add a
> reference to mmal buffer.

Does it make sure to keep the mmal buffer pool alive then? Otherwise a
decoded AVFrame would become invalid after closing and destroying the
decoder.

Why would this need a new option?