[FFmpeg-devel] [PATCH] libavcodec/nvenc.c: copy incoming hwaccel frames instead of ref count increase

[Roman Arzumanyan]

Hello,

This patch makes nvenc copy incoming hwaccel frames instead of ref count 
increase.
It fixes the bug which may happen when on-GPU transcoding is done and encoder 
is set to use B frames.

How to reproduce the bug:
./ffmpeg \
  -hwaccel cuda -hwaccel_output_format cuda \
  -i input.mkv \
  -c:v h264_nvenc -preset p4 -tune hq -bf 3 \
  -y output.mkv

Expected output:
[h264 @ 0x55b14da4b4c0] No decoder surfaces left
[h264 @ 0x55b14da682c0] No decoder surfaces left
[h264 @ 0x55b14da850c0] No decoder surfaces left
[h264 @ 0x55b14daa1ec0] No decoder surfaces left
Error while decoding stream #0:0: Invalid data found when processing input
[h264 @ 0x55b14da2e6c0] No decoder surfaces left
Error while decoding stream #0:0: Invalid data found when processing input
    Last message repeated 1 times


Although fix adds extra CUDA DtoD memcopy, our internal testing results didn't 
show any noticeable difference in transcoding performance.

From c95adcf7d5f5dd787eaa80fa4643e7868f85848e Mon Sep 17 00:00:00 2001
From: Roman Arzumanyan <rarzuman...@nvidia.com>
Date: Tue, 14 Sep 2021 14:03:24 +0300
Subject: [PATCH] nvenc: copy incoming HW frame instead of referencing

---
 libavcodec/nvenc.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
index 815b9429b3..9b4c968179 100644
--- a/libavcodec/nvenc.c
+++ b/libavcodec/nvenc.c
@@ -1849,7 +1849,7 @@ static int nvenc_upload_frame(AVCodecContext *avctx, const AVFrame *frame,
             return reg_idx;
         }
 
-        res = av_frame_ref(nvenc_frame->in_ref, frame);
+        res = av_hwframe_transfer_data(nvenc_frame->in_ref, frame, 0);
         if (res < 0)
             return res;
 
@@ -1858,7 +1858,6 @@ static int nvenc_upload_frame(AVCodecContext *avctx, const AVFrame *frame,
             ctx->registered_frames[reg_idx].in_map.registeredResource = ctx->registered_frames[reg_idx].regptr;
             nv_status = p_nvenc->nvEncMapInputResource(ctx->nvencoder, &ctx->registered_frames[reg_idx].in_map);
             if (nv_status != NV_ENC_SUCCESS) {
-                av_frame_unref(nvenc_frame->in_ref);
                 return nvenc_print_error(avctx, nv_status, "Error mapping an input resource");
             }
         }
@@ -2029,8 +2028,6 @@ static int process_output_surface(AVCodecContext *avctx, AVPacket *pkt, NvencSur
             goto error;
         }
 
-        av_frame_unref(tmpoutsurf->in_ref);
-
         tmpoutsurf->input_surface = NULL;
     }
 
-- 
2.25.1


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