Re: [FFmpeg-devel] [PATCH] avcodec/nvenc: Use CBR filler data consistently across codecs

[Zhao Zhili <quinkblack-at-foxmail.com@ffmpeg.org>]

> On Mar 30, 2025, at 23:33, Kieran Kunhya via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> wrote:
> 
> On Sun, Mar 30, 2025 at 12:04 AM Cameron Gutman <aicommander@gmail.com <mailto:aicommander@gmail.com>> wrote:
>> 
>> Previously, AV1 used filler data with CBR by default while H.264
>> and HEVC did not. Make this consistent by using filler data in
>> CBR mode across all codecs.
>> 
>> Since there are valid reasons to use CBR with or without filler,
>> also add a cbr_padding option to allow users to opt out.
>> 
>> Signed-off-by: Cameron Gutman <aicommander@gmail.com>
>> ---
>> libavcodec/nvenc.c      | 16 +++++++++++++---
>> libavcodec/nvenc.h      |  2 ++
>> libavcodec/nvenc_av1.c  |  2 ++
>> libavcodec/nvenc_h264.c |  4 ++++
>> libavcodec/nvenc_hevc.c |  4 ++++
>> 5 files changed, 25 insertions(+), 3 deletions(-)
>> 
>> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
>> index 0f5e772b3e..41a4dc55f4 100644
>> --- a/libavcodec/nvenc.c
>> +++ b/libavcodec/nvenc.c
>> @@ -1304,7 +1304,12 @@ static av_cold int nvenc_setup_h264_config(AVCodecContext *avctx)
>>     h264->idrPeriod = cc->gopLength;
>> 
>>     if (IS_CBR(cc->rcParams.rateControlMode)) {
>> -        h264->outputBufferingPeriodSEI = 1;
>> +        /* Older SDKs use outputBufferingPeriodSEI to control filler data */
>> +        h264->outputBufferingPeriodSEI = ctx->cbr_padding;
>> +
>> +#ifdef NVENC_HAVE_FILLER_DATA
>> +        h264->enableFillerDataInsertion = ctx->cbr_padding;
>> +#endif
>>     }
>> 
>>     h264->outputPictureTimingSEI = 1;
>> @@ -1503,7 +1508,12 @@ static av_cold int nvenc_setup_hevc_config(AVCodecContext *avctx)
>>     hevc->idrPeriod = cc->gopLength;
>> 
>>     if (IS_CBR(cc->rcParams.rateControlMode)) {
>> -        hevc->outputBufferingPeriodSEI = 1;
>> +        /* Older SDKs use outputBufferingPeriodSEI to control filler data */
>> +        hevc->outputBufferingPeriodSEI = ctx->cbr_padding;
>> +
>> +#ifdef NVENC_HAVE_FILLER_DATA
>> +        hevc->enableFillerDataInsertion = ctx->cbr_padding;
>> +#endif
>>     }
>> 
>>     hevc->outputPictureTimingSEI = 1;
>> @@ -1625,7 +1635,7 @@ static av_cold int nvenc_setup_av1_config(AVCodecContext *avctx)
>>     av1->idrPeriod = cc->gopLength;
>> 
>>     if (IS_CBR(cc->rcParams.rateControlMode)) {
>> -        av1->enableBitstreamPadding = 1;
>> +        av1->enableBitstreamPadding = ctx->cbr_padding;
>>     }
>> 
>>     if (ctx->tile_cols >= 0)
>> diff --git a/libavcodec/nvenc.h b/libavcodec/nvenc.h
>> index e035e123c6..4b12846ed7 100644
>> --- a/libavcodec/nvenc.h
>> +++ b/libavcodec/nvenc.h
>> @@ -61,6 +61,7 @@ typedef void ID3D11Device;
>> #define NVENC_HAVE_MULTIPLE_REF_FRAMES
>> #define NVENC_HAVE_CUSTREAM_PTR
>> #define NVENC_HAVE_GETLASTERRORSTRING
>> +#define NVENC_HAVE_FILLER_DATA
>> #endif
>> 
>> // SDK 10.0 compile time feature checks
>> @@ -309,6 +310,7 @@ typedef struct NvencContext
>>     int unidir_b;
>>     int split_encode_mode;
>>     int mdm, cll;
>> +    int cbr_padding;
>> } NvencContext;
>> 
>> int ff_nvenc_encode_init(AVCodecContext *avctx);
>> diff --git a/libavcodec/nvenc_av1.c b/libavcodec/nvenc_av1.c
>> index 01626113ab..b1b95672f2 100644
>> --- a/libavcodec/nvenc_av1.c
>> +++ b/libavcodec/nvenc_av1.c
>> @@ -156,6 +156,8 @@ static const AVOption options[] = {
>>                                                             OFFSET(extra_sei),    AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>>     { "a53cc",        "Use A53 Closed Captions (if available)", OFFSET(a53_cc),   AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>>     { "s12m_tc",      "Use timecode (if available)",        OFFSET(s12m_tc),      AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
>> +                                                            OFFSET(cbr_padding),  AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>> #ifdef NVENC_HAVE_H264_AND_AV1_TEMPORAL_FILTER
>>     { "tf_level",     "Specifies the strength of the temporal filtering",
>>                                                             OFFSET(tf_level),     AV_OPT_TYPE_INT,   { .i64 = -1 }, -1, INT_MAX, VE, .unit = "tf_level" },
>> diff --git a/libavcodec/nvenc_h264.c b/libavcodec/nvenc_h264.c
>> index 21d25d643a..4845d0422d 100644
>> --- a/libavcodec/nvenc_h264.c
>> +++ b/libavcodec/nvenc_h264.c
>> @@ -231,6 +231,10 @@ static const AVOption options[] = {
>>                                                             OFFSET(max_slice_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, VE },
>>     { "constrained-encoding", "Enable constrainedFrame encoding where each slice in the constrained picture is independent of other slices",
>>                                                             OFFSET(constrained_encoding), AV_OPT_TYPE_BOOL,  { .i64 = 0 }, 0, 1, VE },
>> +#ifdef NVENC_HAVE_FILLER_DATA
>> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
>> +                                                            OFFSET(cbr_padding),  AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>> +#endif
>> #ifdef NVENC_HAVE_H264_AND_AV1_TEMPORAL_FILTER
>>     { "tf_level",     "Specifies the strength of the temporal filtering",
>>                                                             OFFSET(tf_level),     AV_OPT_TYPE_INT,   { .i64 = -1 }, -1, INT_MAX, VE, .unit = "tf_level" },
>> diff --git a/libavcodec/nvenc_hevc.c b/libavcodec/nvenc_hevc.c
>> index c74eca9bb3..8648f4f3a9 100644
>> --- a/libavcodec/nvenc_hevc.c
>> +++ b/libavcodec/nvenc_hevc.c
>> @@ -206,6 +206,10 @@ static const AVOption options[] = {
>>                                                             OFFSET(max_slice_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, VE },
>>     { "constrained-encoding", "Enable constrainedFrame encoding where each slice in the constrained picture is independent of other slices",
>>                                                             OFFSET(constrained_encoding), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
>> +#ifdef NVENC_HAVE_FILLER_DATA
>> +    { "cbr_padding",  "Pad the bitstream to ensure bitrate does not drop below the target in CBR mode",
>> +                                                            OFFSET(cbr_padding),  AV_OPT_TYPE_BOOL,  { .i64 = 1 }, 0, 1, VE },
>> +#endif
>> #ifdef NVENC_HAVE_TEMPORAL_FILTER
>>     { "tf_level",     "Specifies the strength of the temporal filtering",
>>                                                             OFFSET(tf_level),     AV_OPT_TYPE_INT,   { .i64 = -1 }, -1, INT_MAX, VE, .unit = "tf_level" },
>> --
>> 2.49.0
> 
> 
> This should be off by default in FFmpeg. We don't do this in any other encoder.

I agree.

> 
> Kieran
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