mpeg2_metadata, cbs_mpeg2: Fix handling of colour_description

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
possible.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/libavcodec/mpeg2_metadata_bsf.c b/libavcodec/mpeg2_metadata_bsf.c
index 6779ffd..3f371a0 100644
--- a/libavcodec/mpeg2_metadata_bsf.c
+++ b/libavcodec/mpeg2_metadata_bsf.c
@@ -213,6 +213,18 @@ 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
+
     err = ff_cbs_init(&ctx->cbc, AV_CODEC_ID_MPEG2VIDEO, bsf);
     if (err < 0)
         return err;