[FFmpeg-devel] [PATCH 1/2] avcodec/cbs_av1: add a function to get a payload size without trailing zero bytes

[Mark Thompson]

On 13/04/2019 20:21, James Almer wrote:
> Factor it out from cbs_av1_read_metadata_itut_t35()
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavcodec/cbs_av1.c                 | 11 +++++++++++
>  libavcodec/cbs_av1_syntax_template.c | 10 +---------
>  2 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
> index f02cca2dad..0c03ca28af 100644
> --- a/libavcodec/cbs_av1.c
> +++ b/libavcodec/cbs_av1.c
> @@ -574,6 +574,17 @@ static int cbs_av1_get_relative_dist(const AV1RawSequenceHeader *seq,
>      return diff;
>  }
>  
> +static int cbs_av1_get_payload_bytes_left(GetBitContext *gbc)
> +{
> +    GetBitContext tmp = *gbc;
> +    int size = 0;
> +    for (int i = 0; get_bits_left(&tmp) >= 8; i++) {
> +        if (get_bits(&tmp, 8))
> +            size = i;
> +    }
> +    return size;
> +}

I don't think it matters because of get_bits, but maybe this should be size_t?

> +
>  
>  #define HEADER(name) do { \
>          ff_cbs_trace_header(ctx, name); \
> diff --git a/libavcodec/cbs_av1_syntax_template.c b/libavcodec/cbs_av1_syntax_template.c
> index 76eb90b279..56009145e8 100644
> --- a/libavcodec/cbs_av1_syntax_template.c
> +++ b/libavcodec/cbs_av1_syntax_template.c
> @@ -1674,15 +1674,7 @@ static int FUNC(metadata_itut_t35)(CodedBitstreamContext *ctx, RWContext *rw,
>  #ifdef READ
>      // The payload runs up to the start of the trailing bits, but there might
>      // be arbitrarily many trailing zeroes so we need to read through twice.
> -    {
> -        GetBitContext tmp = *rw;
> -        current->payload_size = 0;
> -        for (i = 0; get_bits_left(rw) >= 8; i++) {
> -            if (get_bits(rw, 8))
> -                current->payload_size = i;
> -        }
> -        *rw = tmp;
> -    }
> +    current->payload_size = cbs_av1_get_payload_bytes_left(rw);
>  
>      current->payload_ref = av_buffer_alloc(current->payload_size);
>      if (!current->payload_ref)
> 

LGTM in any case.

Thanks,

- Mark