avformat/hls: add support for alternative renditions

HLS protocol version 4 added alternative renditions to the
specification (e.g. alternative audio tracks).

The EXT-X-MEDIA tags can also contain metadata for "renditions" (i.e.
tracks) of the main Media Playlist.

Add support for those.

Note that the same rendition (AVStream) may be associated with multiple
variants (AVPrograms).

Alternative subtitle tracks will require additional work and are
therefore not enabled yet.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: always return EOF for unneeded playlist streams

Even if we returned AVERROR_EOF previously due to playlist no longer
being needed, we may still be called again, and we do not want to
trigger a segment download in that case.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: add support for byte-ranged segments

Add support for EXT-X-BYTERANGE added in HLS protocol v4.

v2: Better comment explaining ffurl_seek call and fix cur_seg_offset not
being updated.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: add some logging messages

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: split read_from_url() out of read_data()

Useful for ID3 parsing.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: parse ID3 timestamps for elementary audio streams

HLS provides MPEG TS timestamps via ID3 tags in the beginning of each
segment of elementary audio streams.

v2: fix issues with streams that have multiple ID3 tags

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: track seeking on a per-playlist basis

Seeking needs to be tracked on a per-playlist basis, since the resyncing
code in hls_read_packet() has to sync each playlist to the seek
timestamp instead of stopping after the first playlist has reached it.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: improve segment selection when restarting list reception

Improve selection of the segment sequence number when restarting the
reception of a playlist after it was suspended due to being unneeded
(due to discard flags).

The current code assumes that each playlist contains matching data with
the same sequence number, while spec 3.4.3 specifically says that that
is not the case. Often subtitle playlists also have longer target
durations as well, causing the selection to be completely wrong.

Instead prefer using the playlist segment duration information for
non-live playlists, and other means if that is not possible.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: avoid unnecessary segment retrievals

Check if the playlist is still needed just before requesting the next
segment instead of after exhausting the previous segment.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: do not care about stream start timestamps

While selecting a packet to return to caller in read_packet(), the code
corrects the timestamps for starting timestamps.

However, this is wrong, since for live streams the initial timestamps
might differ just because of the time delay between the retrieval of the
various Media Playlists.

Fortunately, spec 6.2.4 mandates that all variant streams must have
matching timestamps, so we do not need to correct for initial
timestamps.

Drop the correction code.

Note that ID3 timestamps were previously ignored, so this code was
previously actually needed.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: do not use sequence numbers for packet ordering

As per spec 3.4.3 ("A client MUST NOT assume that segments with the same
sequence number in different Media Playlists contain matching content.")
we cannot use sequence numbers for packet ordering.

This can be seen e.g. in the subtitle streams of
bipbop_16x9_variant.m3u8 that have considerably longer segments and
therefore different numbering.

Since the code now exclusively syncs using timestamps that may wrap, add
some additional checking for that.

According to the HLS spec all the timestamps should be in 33-bit MPEG
format and synced together.

v2: cleaner wrap detection
v3: further wrap detection improvements

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: factor identical playlist allocations out of parse_playlist

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: open playlists immediately when AVDISCARD_ALL is dropped

Do not try to delay opening newly required playlists until a segment
switch. Applications expect that newly selected undiscarded streams are
available immediately, especially with alternative rendition streams
(selectable audio/subtitle tracks).

One might think that delaying variant stream switch until a segment
switch would allow a "seamless" switch without us having to download a
specific segment from two different variant playlists. However, that is
not the case, since the application would have to keep the previous
stream available (undiscarded) until the first packet of the newly
selected stream arrives, but by that time the demuxer would have already
downloaded the next segment of both variants.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: properly take stream_index into account when seeking

Properly take stream_index into account so that a keyframe will be
looked for in the specified stream_index only.

Similarly, only check timestamp validity against the specified
stream_index.

Also remove code for stream_index == -1 case which does not actually
happen as it is handled by generic code.

This is based on an initial patch by James Deng.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: flush the subdemuxer when seeking

Since we are basically seeking the AVIOContext under the subdemuxer, we
need to flush the subdemuxer to avoid old packets from being read from
the packet queue after the seek.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
avformat/hls: support for seeking on event playlists

This allows clients to seek between first played segment
and the last one in the live stream playlist with #EXT-X-PLAYLIST-TYPE:EVENT attribute.
avcodec/vp8: fix checking vp7_feature_value_size

Fixes CID1197061

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/oggdec: check for av_packet_new_side_data() failure

Fixes CID1197062
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/oggdec/ogg_read_packet(): factorize failure code path

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>