[FFmpeg-devel] [RFC PATCH 3/4] avcodec/hevcdec: add nuh_layer_id option

[James Almer]

On 1/5/2023 1:14 PM, Zhao Zhili wrote:
> From: Zhao Zhili <zhilizhao at tencent.com>
> 
> It can be used to decode selected independent non-base layer. One
> use case is alpha layer decoding.
> 
> Signed-off-by: Zhao Zhili <zhilizhao at tencent.com>
> ---
>   libavcodec/hevcdec.c | 20 +++++++++++++++++++-
>   libavcodec/version.h |  2 +-
>   2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
> index 567e8d81d4..9641922834 100644
> --- a/libavcodec/hevcdec.c
> +++ b/libavcodec/hevcdec.c
> @@ -3216,7 +3216,8 @@ static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
>   
>           if (s->avctx->skip_frame >= AVDISCARD_ALL ||
>               (s->avctx->skip_frame >= AVDISCARD_NONREF
> -            && ff_hevc_nal_is_nonref(nal->type)) || nal->nuh_layer_id > 0)
> +            && ff_hevc_nal_is_nonref(nal->type)) ||
> +            nal->nuh_layer_id != s->nuh_layer_id)
>               continue;
>   
>           ret = decode_nal_unit(s, nal);
> @@ -3637,6 +3638,21 @@ static av_cold int hevc_decode_init(AVCodecContext *avctx)
>       HEVCContext *s = avctx->priv_data;
>       int ret;
>   
> +    if (s->nuh_layer_id > 0) {
> +        if (avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {
> +            av_log(avctx, AV_LOG_ERROR,
> +                    "Decode selected nuh_layer_id is undef development. "
> +                    "Use -strict -2 to use it anyway.\n");

"Undef development"? Does decoding of these non-base layers work or not? 
One thing is something being experimental (thus known to be working in 
at least some cases, even if not spec compliant), and another is 
enabling something we don't know if it's going to work or not at all.

> +            return AVERROR(EINVAL);
> +        }
> +
> +        if (avctx->hwaccel) {
> +            av_log(avctx, AV_LOG_ERROR,
> +                    "Decode selected nuh_layer_id doesn't work with hwaccel.\n");
> +            return AVERROR(EINVAL);
> +        }
> +    }
> +
>       if (avctx->active_thread_type & FF_THREAD_SLICE) {
>           s->threads_number = avctx->thread_count;
>           ret = ff_slice_thread_init_progress(avctx);
> @@ -3691,6 +3707,8 @@ static const AVOption options[] = {
>           AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, PAR },
>       { "strict-displaywin", "stricly apply default display window size", OFFSET(apply_defdispwin),
>           AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, PAR },
> +    { "nuh_layer_id", "Select which nuh_layer_id to decode (only works with INBL)", OFFSET(nuh_layer_id),
> +        AV_OPT_TYPE_INT,  {.i64 = 0}, 0, 62, PAR },
>       { NULL },
>   };
>   
> diff --git a/libavcodec/version.h b/libavcodec/version.h
> index 6b8a1dbb79..15f7c3fe3d 100644
> --- a/libavcodec/version.h
> +++ b/libavcodec/version.h
> @@ -30,7 +30,7 @@
>   #include "version_major.h"
>   
>   #define LIBAVCODEC_VERSION_MINOR  56
> -#define LIBAVCODEC_VERSION_MICRO 100
> +#define LIBAVCODEC_VERSION_MICRO 101
>   
>   #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
>                                                  LIBAVCODEC_VERSION_MINOR, \