hevc_nvenc / b_ref_mode each is not working

[enctac]

When using "-c:v hevc_nvenc", "-b_ref_mode each" option is not working by saying out:
Each B frame as reference is not supported

How to reproduce:

% ffmpeg.exe -y -i input.mp4 -c:v hevc_nvenc -bf 3 -b_ref_mode each -an output.mp4

Memo:

"-b_ref_mode each" needs Turing GPU and "-c:v hevc_nvenc".
h264_nvenc doesn't support "-b_ref_mode each". (#7301)

Examples:

​Case1(English):ffmpeg-20200311-36aaee2-win64-static, GPU:RTX 2080 SUPER (Driver:442.59)

​Case2(Japanese):ffmpeg 4.3(Zeranoe), GPU: 1660 SUPER (Driver:446.14)

Comment:

Source Code:

​https://github.com/FFmpeg/FFmpeg/blob/master/libavcodec/nvenc.c#L425

NV_ENC_CAPS_SUPPORT_BFRAME_REF_MODE:

​https://github.com/FFmpeg/nv-codec-headers/blob/master/include/ffnvcodec/nvEncodeAPI.h#L1089

When GPU supports "each" and "middle", NV_ENC_CAPS_SUPPORT_BFRAME_REF_MODE maybe returns "3" (0x01 | 0x02).

ref. ​RTX2070 features ("Codec: H.265/HEVC -> B Ref Mode" is "3")

But ​code is:

ret = nvenc_check_cap(avctx, NV_ENC_CAPS_SUPPORT_BFRAME_REF_MODE);
if (ctx->b_ref_mode == NV_ENC_BFRAME_REF_MODE_EACH && ret != 1) {

av_log(avctx, AV_LOG_WARNING, "Each B frame as reference is not supported\n");
return AVERROR(ENOSYS);

} else if ...

I don't have Turing GPU.
Please check and fix this problem.

[Balling]

That is true. My 2080 Ti says -c:v hevc_nvenc -bf 3 -b_ref_mode each is not supported... Hmmm.

[Balling]

First, we need to check that avctx HEVC is indeed 3 and avctx AVC returns 2. Also we need to change comment \n 2 : only Middle B-frame as reference is supported to "Middle B-frame as reference is supported to " in ​​https://github.com/FFmpeg/nv-codec-headers/blob/master/include/ffnvcodec/nvEncodeAPI.h#L1089

[Balling]

Should be fixed in 466c14d10728cd315c60e602ffe3797e7dd0c3d3
P.S. I tested it, it works.