Re: [FFmpeg-devel] [PATCH v5 3/8] avcodec/cbs_av1: Allow specifying obu size byte length

[Neal Gompa <ngompa13@gmail.com>]

On Mon, Sep 11, 2023 at 3:53 AM <fei.w.wang-at-intel.com@ffmpeg.org> wrote:
>
> From: Fei Wang <fei.w.wang@intel.com>
>
> Signed-off-by: Fei Wang <fei.w.wang@intel.com>
> ---
>  libavcodec/cbs_av1.c | 30 +++++++++++++++++++++---------
>  libavcodec/cbs_av1.h |  1 +
>  2 files changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
> index 6c478603f1..4e687ace79 100644
> --- a/libavcodec/cbs_av1.c
> +++ b/libavcodec/cbs_av1.c
> @@ -138,15 +138,19 @@ static int cbs_av1_read_leb128(CodedBitstreamContext *ctx, GetBitContext *gbc,
>      return 0;
>  }
>
> +/** Minimum byte length will be used to indicate the len128 of value if byte_len is 0. */
>  static int cbs_av1_write_leb128(CodedBitstreamContext *ctx, PutBitContext *pbc,
> -                                const char *name, uint64_t value)
> +                                const char *name, uint64_t value, uint8_t byte_len)
>  {
>      int len, i;
>      uint8_t byte;
>
>      CBS_TRACE_WRITE_START();
>
> -    len = (av_log2(value) + 7) / 7;
> +    if (byte_len)
> +        av_assert0(byte_len >= (av_log2(value) + 7) / 7);
> +
> +    len = byte_len ? byte_len : (av_log2(value) + 7) / 7;
>
>      for (i = 0; i < len; i++) {
>          if (put_bits_left(pbc) < 8)
> @@ -618,7 +622,7 @@ static size_t cbs_av1_get_payload_bytes_left(GetBitContext *gbc)
>      } while (0)
>
>  #define leb128(name) do { \
> -        CHECK(cbs_av1_write_leb128(ctx, rw, #name, current->name)); \
> +        CHECK(cbs_av1_write_leb128(ctx, rw, #name, current->name, 0)); \
>      } while (0)
>
>  #define infer(name, value) do { \
> @@ -1002,9 +1006,14 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
>
>      if (obu->header.obu_has_size_field) {
>          pbc_tmp = *pbc;
> -        // Add space for the size field to fill later.
> -        put_bits32(pbc, 0);
> -        put_bits32(pbc, 0);
> +        if (obu->obu_size_byte_len) {
> +            for (int i = 0; i < obu->obu_size_byte_len; i++)
> +                put_bits(pbc, 8, 0);
> +        } else {
> +            // Add space for the size field to fill later.
> +            put_bits32(pbc, 0);
> +            put_bits32(pbc, 0);
> +        }
>      }
>
>      td = NULL;
> @@ -1124,7 +1133,7 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
>      end_pos   /= 8;
>
>      *pbc = pbc_tmp;
> -    err = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size);
> +    err = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size, obu->obu_size_byte_len);
>      if (err < 0)
>          goto error;
>
> @@ -1141,8 +1150,11 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
>      }
>
>      if (obu->obu_size > 0) {
> -        memmove(pbc->buf + data_pos,
> -                pbc->buf + start_pos, header_size);
> +        if (!obu->obu_size_byte_len) {
> +            obu->obu_size_byte_len = start_pos - data_pos;
> +            memmove(pbc->buf + data_pos,
> +                    pbc->buf + start_pos, header_size);
> +        }
>          skip_put_bytes(pbc, header_size);
>
>          if (td) {
> diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
> index 64dfdce9c4..a9e2d2284f 100644
> --- a/libavcodec/cbs_av1.h
> +++ b/libavcodec/cbs_av1.h
> @@ -401,6 +401,7 @@ typedef struct AV1RawOBU {
>      AV1RawOBUHeader header;
>
>      size_t obu_size;
> +    uint8_t obu_size_byte_len;
>
>      union {
>          AV1RawSequenceHeader sequence_header;
> --
> 2.25.1
>

Code looks good to me.

Reviewed-by: Neal Gompa <ngompa13@gmail.com>



-- 
真実はいつも一つ！/ Always, there's only one truth!
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