On 22/05/2019 02:04, Andreas Rheinhardt wrote:
> If a sequence display extension is read with colour_description equal to
> zero, but a user wants to add one or more of the colour_description
> elements, then the colour_description elements the user did not explicitly
> request to be set are set to zero and not to the value equal to
> unknown/unspecified (namely 2). A value of zero is not only inappropriate,
> but explicitly forbidden. This is fixed by inferring the right default
> values during the reading process if the elements are absent; moreover,
> changing any of the colour_description elements to zero is now no longer
> permitted.
>
> Furthermore, if a sequence display extension has to be added, the
> earlier code set some fields to their default value twice. This has been
> changed, too.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
> ---
> libavcodec/cbs_mpeg2.c | 15 +++++++++++++++
> libavcodec/cbs_mpeg2_syntax_template.c | 4 ++++
> libavcodec/mpeg2_metadata_bsf.c | 18 ++++++++++++------
> 3 files changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
> index 1d319e0947..437eac88a3 100644
> --- a/libavcodec/cbs_mpeg2.c
> +++ b/libavcodec/cbs_mpeg2.c
> @@ -71,6 +71,10 @@
> (get_bits_left(rw) >= width && \
> (var = show_bits(rw, width)) == (compare))
>
> +#define infer(name, value) do { \
> + current->name = value; \
> + } while (0)
> +
> #include "cbs_mpeg2_syntax_template.c"
>
> #undef READ
> @@ -79,6 +83,7 @@
> #undef xui
> #undef marker_bit
> #undef nextbits
> +#undef infer
>
>
> #define WRITE
> @@ -97,6 +102,15 @@
>
> #define nextbits(width, compare, var) (var)
>
> +#define infer(name, value) do { \
> + if (current->name != (value)) { \
> + av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
> + "%s does not match inferred value: " \
> + "%"PRId64", but should be %"PRId64".\n", \
> + #name, (int64_t)current->name, (int64_t)(value)); \
> + } \
> + } while (0)
> +
> #include "cbs_mpeg2_syntax_template.c"
>
> #undef READ
> @@ -105,6 +119,7 @@
> #undef xui
> #undef marker_bit
> #undef nextbits
> +#undef infer
>
>
> static void cbs_mpeg2_free_user_data(void *unit, uint8_t *content)
> diff --git a/libavcodec/cbs_mpeg2_syntax_template.c
> b/libavcodec/cbs_mpeg2_syntax_template.c
> index b9d53682fe..87db0ad039 100644
> --- a/libavcodec/cbs_mpeg2_syntax_template.c
> +++ b/libavcodec/cbs_mpeg2_syntax_template.c
> @@ -144,6 +144,10 @@ static int
> FUNC(sequence_display_extension)(CodedBitstreamContext *ctx, RWContex
> uir(8, transfer_characteristics);
> uir(8, matrix_coefficients);
> #endif
> + } else {
> + infer(colour_primaries, 2);
> + infer(transfer_characteristics, 2);
> + infer(matrix_coefficients, 2);
> }
>
> ui(14, display_horizontal_size);
> diff --git a/libavcodec/mpeg2_metadata_bsf.c b/libavcodec/mpeg2_metadata_bsf.c
> index ba3a74afda..5aed41a008 100644
> --- a/libavcodec/mpeg2_metadata_bsf.c
> +++ b/libavcodec/mpeg2_metadata_bsf.c
> @@ -147,18 +147,12 @@ static int mpeg2_metadata_update_fragment(AVBSFContext
> *bsf,
>
> if (ctx->colour_primaries >= 0)
> sde->colour_primaries = ctx->colour_primaries;
> - else if (add_sde)
> - sde->colour_primaries = 2;
>
> if (ctx->transfer_characteristics >= 0)
> sde->transfer_characteristics =
> ctx->transfer_characteristics;
> - else if (add_sde)
> - sde->transfer_characteristics = 2;
>
> if (ctx->matrix_coefficients >= 0)
> sde->matrix_coefficients = ctx->matrix_coefficients;
> - else if (add_sde)
> - sde->matrix_coefficients = 2;
> }
> }
>
> @@ -229,6 +223,18 @@ static int mpeg2_metadata_init(AVBSFContext *bsf)
> CodedBitstreamFragment *frag = &ctx->fragment;
> int err;
>
> +#define VALIDITY_CHECK(name) do { \
> + if (!ctx->name) { \
> + av_log(bsf, AV_LOG_ERROR, "The value 0 for %s is " \
> + "forbidden.\n", #name); \
> + return AVERROR(EINVAL); \
> + } \
> + } while (0)
> + VALIDITY_CHECK(colour_primaries);
> + VALIDITY_CHECK(transfer_characteristics);
> + VALIDITY_CHECK(matrix_coefficients);
> +#undef VALIDITY_CHECK
Perhaps we could use the normal option checking to enforce this? Suppose we
change the range from [-1, 255] to [0, 255] and make the do-nothing default
value 0. Then the checks above become ctx->colour_primaries > 0 and this
separate test is not needed.
> +
> err = ff_cbs_init(&ctx->cbc, AV_CODEC_ID_MPEG2VIDEO, bsf);
> if (err < 0)
> return err;
>
- Mark
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