mån 2021-05-24 klockan 12:30 +0200 skrev emcodem:
> Added support for reading Start Timecode from Footer (if any).
> Specifically targets Omneon 6.4.3.0 but also works on other Versions and
> Vendors, e.g. when Header is OpenIncomplete.
> Function mxf_resolve_strong_ref_reverse can potentially be re-used for
> getting other values like Duration and
> Origin from Footer.
This needs a sample and a test
> ---
> libavformat/mxfdec.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> index 3bf480a3a6..557e01f8ed 100644
> --- a/libavformat/mxfdec.c
> +++ b/libavformat/mxfdec.c
> @@ -1396,6 +1396,19 @@ static const MXFCodecUL *mxf_get_codec_ul(const
> MXFCodecUL *uls, UID *uid)
> return uls;
> }
>
> +static void *mxf_resolve_strong_ref_reverse(MXFContext *mxf, UID
> *strong_ref, enum MXFMetadataSetType type)
This and mxf_resolve_strong_ref() could maybe be merged to one function
with an "int dir" option, and mxf_resolve_strong_ref() just calling it
with the value 1.
> +{
> + int i;
> + if (!strong_ref)
> + return NULL;
> + for (i = mxf->metadata_sets_count-1; i >= 0 ; i--) {
> + if (!memcmp(*strong_ref, mxf->metadata_sets[i]->uid, 16) &&
> + (type == AnyType || mxf->metadata_sets[i]->type == type)) {
> + return mxf->metadata_sets[i];
> + }
> + }
> + return NULL;
> +}
Missing newline, but I can add that locally
> static void *mxf_resolve_strong_ref(MXFContext *mxf, UID *strong_ref, enum
> MXFMetadataSetType type)
> {
> int i;
> @@ -2328,8 +2341,15 @@ static int mxf_parse_structural_metadata(MXFContext
> *mxf)
> continue;
>
> mxf_tc = (MXFTimecodeComponent*)component;
> + if (mxf_tc->start_frame <= 0) {
I feel like this should trigger on OpenIncomplete instead. I wouldn't
be surprised if start_frame < 0 is perfectly valid.
> + if (mxf_tc->start_frame <= 0) {
> + av_log(mxf->fc, AV_LOG_TRACE, "Header Start Timecode was
> %d, trying reversed parsing\n",mxf_tc->start_frame);
> + component = mxf_resolve_strong_ref_reverse(mxf,
> &material_track->sequence->structural_components_refs[j], TimecodeComponent);
> + mxf_tc = (MXFTimecodeComponent*)component;
Wrong indent. I was also going to comment that mxf_tc might end up NULL
here but it can't since it's non-NULL when resolving in the forward
direction.
/Tomas
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