On 25/03/2019 14:22, James Almer wrote:
> Based on itut_t35 Matadata OBU parsing code.
>
> Signed-off-by: James Almer <jamr...@gmail.com>
> ---
> libavcodec/cbs_av1.c | 20 +++++++++++++++++
> libavcodec/cbs_av1.h | 7 ++++++
> libavcodec/cbs_av1_syntax_template.c | 32 ++++++++++++++++++++++++++++
> 3 files changed, 59 insertions(+)
>
> diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
> index 02f168b58d..22330eabf3 100644
> --- a/libavcodec/cbs_av1.c
> +++ b/libavcodec/cbs_av1.c
> @@ -857,6 +857,11 @@ static void cbs_av1_free_tile_data(AV1RawTileData *td)
> av_buffer_unref(&td->data_ref);
> }
>
> +static void cbs_av1_free_padding(AV1RawPadding *pd)
> +{
> + av_buffer_unref(&pd->payload_ref);
> +}
> +
> static void cbs_av1_free_metadata(AV1RawMetadata *md)
> {
> switch (md->metadata_type) {
> @@ -883,6 +888,9 @@ static void cbs_av1_free_obu(void *unit, uint8_t *content)
> case AV1_OBU_METADATA:
> cbs_av1_free_metadata(&obu->obu.metadata);
> break;
> + case AV1_OBU_PADDING:
> + cbs_av1_free_padding(&obu->obu.padding);
> + break;
> }
>
> av_freep(&obu);
> @@ -1057,6 +1065,12 @@ static int cbs_av1_read_unit(CodedBitstreamContext
> *ctx,
> }
> break;
> case AV1_OBU_PADDING:
> + {
> + err = cbs_av1_read_padding(ctx, &gbc, &obu->obu.padding);
> + if (err < 0)
> + return err;
> + }
> + break;
> default:
> return AVERROR(ENOSYS);
> }
> @@ -1182,6 +1196,12 @@ static int cbs_av1_write_obu(CodedBitstreamContext
> *ctx,
> }
> break;
> case AV1_OBU_PADDING:
> + {
> + err = cbs_av1_write_padding(ctx, pbc, &obu->obu.padding);
> + if (err < 0)
> + return err;
> + }
> + break;
> default:
> return AVERROR(ENOSYS);
> }
> diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
> index 71ceff9427..e799964b72 100644
> --- a/libavcodec/cbs_av1.h
> +++ b/libavcodec/cbs_av1.h
> @@ -364,6 +364,12 @@ typedef struct AV1RawMetadata {
> } metadata;
> } AV1RawMetadata;
>
> +typedef struct AV1RawPadding {
> + uint8_t *payload;
> + size_t payload_size;
> + AVBufferRef *payload_ref;
> +} AV1RawPadding;
> +
>
> typedef struct AV1RawOBU {
> AV1RawOBUHeader header;
> @@ -377,6 +383,7 @@ typedef struct AV1RawOBU {
> AV1RawTileGroup tile_group;
> AV1RawTileList tile_list;
> AV1RawMetadata metadata;
> + AV1RawPadding padding;
> } obu;
> } AV1RawOBU;
>
> diff --git a/libavcodec/cbs_av1_syntax_template.c
> b/libavcodec/cbs_av1_syntax_template.c
> index 76eb90b279..a6cafdd99f 100644
> --- a/libavcodec/cbs_av1_syntax_template.c
> +++ b/libavcodec/cbs_av1_syntax_template.c
> @@ -1763,3 +1763,35 @@ static int FUNC(metadata_obu)(CodedBitstreamContext
> *ctx, RWContext *rw,
>
> return 0;
> }
> +
> +static int FUNC(padding)(CodedBitstreamContext *ctx, RWContext *rw,
> + AV1RawPadding *current)
> +{
> + int i, err;
> +
> + HEADER("Padding");
> +
> +#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_ref = av_buffer_alloc(current->payload_size);
> + if (!current->payload_ref)
> + return AVERROR(ENOMEM);
> + current->payload = current->payload_ref->data;
> + }
> +#endif
That looks factorisable. Can we make a "measure length of payload and allocate
buffer for it" function and use it in metadata_itu_t35 as well?
> +
> + for (i = 0; i < current->payload_size; i++)
> + xf(8, obu_padding_byte[i], current->payload[i], 0x00, 0xff, 1, i);
> +
> + return 0;
> +}
>
Code looks sensible, but could you explain a bit more about why this is
helpful. Is there a use-case for preserving the actual padding bytes? If
that's some sort of CBR application, is it actually going to need to preserve
the trailing zeroes as well?
Thanks,
- Mark
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