James Almer (12021-03-23): > Signed-off-by: James Almer <jamr...@gmail.com> > --- > Following "lavf: move AVStream.*index_entries* to AVStreamInternal", it was > revealed that some library users apparently found these fields useful and were > accessing them despite not being public. > This patch introduces a few functions to recover this functionality in a > proper > and supported way. >
> We can't simply return a const pointer to the corresponding AVIndexEntry in
> the
> array because it may change at any time by for example calling
> av_add_index_entry(), so it's either a copy of the AVIndexEntry, or adding
> half
> a dozen output parameters to the function signature for each field in
> AVIndexEntry.
We can return a const pointer to the AVIndexEntry if we document it:
Warning: the returned pointer is only valid until the next
operation that may modify the AVStream or the AVFormatContext it
belongs to. Accessing it after av_read_frame() or other
functions results in undefined behavior.
Users can still copy it immediately if they need it longer.
>
> libavformat/avformat.h | 39 +++++++++++++++++++++++++++++++++++++++
> libavformat/utils.c | 32 ++++++++++++++++++++++++++++++++
> 2 files changed, 71 insertions(+)
>
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 765bc3b6f5..ac8b57149e 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -2754,6 +2754,45 @@ int av_find_default_stream_index(AVFormatContext *s);
> */
> int av_index_search_timestamp(AVStream *st, int64_t timestamp, int flags);
>
> +/**
> + * Get the index entry count for the given AVStream.
> + *
> + * @param st stream
> + * @return the number of index entries in the stream
> + */
> +int av_index_get_entries_count(AVStream *st);
> +
> +/**
> + * Get the AVIndexEntry corresponding to the given index.
> + *
> + * @param st stream containing the requested AVIndexEntry
> + * @param index_entry pointer to an AVIndexEntry where to store the entry.
> On failure,
> + * or if the index entry could not be found, this struct
> will remain
> + * untouched
> + * @param idx the desired index
> + * @return >= 0 on success. AVERROR(ENOENT) if no entry for the requested
> index could
> + be found. other negative AVERROR codes on failure.
> + */
> +int av_index_get_entry(AVStream *st, AVIndexEntry *index_entry, int idx);
> +
> +/**
> + * Get the AVIndexEntry corresponding to the given timestamp.
> + *
> + * @param st stream containing the requested AVIndexEntry
> + * @param index_entry pointer to an AVIndexEntry where to store the entry.
> On failure,
> + * or if the index entry could not be found, this struct
> will remain
> + * untouched
> + * @param timestamp timestamp to retrieve the index entry for
> + * @param flags if AVSEEK_FLAG_BACKWARD then the returned entry will
> correspond
> + * to the timestamp which is <= the requested one, if
> backward
> + * is 0, then it will be >=
> + * if AVSEEK_FLAG_ANY seek to any frame, only keyframes
> otherwise
> + * @return >= 0 on success. AVERROR(ENOENT) if no entry for the requested
> timestamp could
> + * be found. other negative AVERROR codes on failure.
> + */
> +int av_index_get_entry_from_timestamp(AVStream *st, AVIndexEntry
> *index_entry,
> + int64_t wanted_timestamp, int flags);
> +
> /**
> * Add an index entry into a sorted list. Update the entry if the list
> * already contains it.
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index f31826f2ea..4e7a8bf23e 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -2129,6 +2129,38 @@ int av_index_search_timestamp(AVStream *st, int64_t
> wanted_timestamp, int flags)
> wanted_timestamp, flags);
> }
>
> +int av_index_get_entries_count(AVStream *st)
> +{
> + return st->internal->nb_index_entries;
> +}
> +
> +int av_index_get_entry(AVStream *st, AVIndexEntry *index_entry, int idx)
> +{
> + if (idx < 0)
> + return AVERROR(EINVAL);
Make idx unsigned.
> + if (idx >= st->internal->nb_index_entries)
> + return AVERROR(ENOENT);
> +
> + memcpy(index_entry, &st->internal->index_entries[idx],
> sizeof(*index_entry));
Why not using an assignment?
But this makes sizeof(AVIndexEntry) part of the ABI. Probably not what
we want.
> +
> + return 0;
> +}
> +
> +int av_index_get_entry_from_timestamp(AVStream *st, AVIndexEntry
> *index_entry,
> + int64_t wanted_timestamp, int flags)
> +{
> + int idx = ff_index_search_timestamp(st->internal->index_entries,
> + st->internal->nb_index_entries,
> + wanted_timestamp, flags);
> +
> + if (idx < 0)
> + return AVERROR(ENOENT);
> +
> + memcpy(index_entry, &st->internal->index_entries[idx],
> sizeof(*index_entry));
Same, of course.
> +
> + return 0;
> +}
> +
> static int64_t ff_read_timestamp(AVFormatContext *s, int stream_index,
> int64_t *ppos, int64_t pos_limit,
> int64_t (*read_timestamp)(struct
> AVFormatContext *, int , int64_t *, int64_t ))
> {
Regards,
--
Nicolas George
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