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avformat/hls: add #EXT-X-START tag support by prefer_x_start opt

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Reviewed-by: Steven Liu <liuqi05@kuaishou.com>
Signed-off-by: Li Kai <wolfleekay@gmail.com>
This commit is contained in:
Li Kai 2022-06-23 00:55:38 +08:00 committed by Steven Liu
parent 1af3698296
commit df8ad4e391
2 changed files with 61 additions and 2 deletions
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3
doc/demuxers.texi
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@ -373,6 +373,9 @@ It accepts the following options:
@item live_start_index
segment index to start live streams at (negative values are from the end).
@item prefer_x_start
prefer to use #EXT-X-START if it's in playlist instead of live_start_index.
@item allowed_extensions
',' separated list of file extensions that hls is allowed to access.

60
libavformat/hls.c
View File

@ -120,6 +120,8 @@ struct playlist {
enum PlaylistType type;
int64_t target_duration;
int64_t start_seq_no;
int time_offset_flag;
int64_t start_time_offset;
int n_segments;
struct segment **segments;
int needed;
@ -211,6 +213,7 @@ typedef struct HLSContext {
int64_t cur_seq_no;
int m3u8_hold_counters;
int live_start_index;
int prefer_x_start;
int first_packet;
int64_t first_timestamp;
int64_t cur_timestamp;
@ -889,6 +892,21 @@ static int parse_playlist(HLSContext *c, const char *url,
cur_init_section->key = NULL;
}
} else if (av_strstart(line, "#EXT-X-START:", &ptr)) {
const char *time_offset_value = NULL;
ret = ensure_playlist(c, &pls, url);
if (ret < 0) {
goto fail;
}
if (av_strstart(ptr, "TIME-OFFSET=", &time_offset_value)) {
float offset = strtof(time_offset_value, NULL);
pls->start_time_offset = offset * AV_TIME_BASE;
pls->time_offset_flag = 1;
} else {
av_log(c->ctx, AV_LOG_WARNING, "#EXT-X-START value is"
"invalid, it will be ignored");
continue;
}
} else if (av_strstart(line, "#EXT-X-ENDLIST", &ptr)) {
if (pls)
pls->finished = 1;
@ -1722,9 +1740,45 @@ static int64_t select_cur_seq_no(HLSContext *c, struct playlist *pls)
/* If this is a live stream, start live_start_index segments from the
* start or end */
if (c->live_start_index < 0)
return pls->start_seq_no + FFMAX(pls->n_segments + c->live_start_index, 0);
seq_no = pls->start_seq_no + FFMAX(pls->n_segments +
c->live_start_index, 0);
else
return pls->start_seq_no + FFMIN(c->live_start_index, pls->n_segments - 1);
seq_no = pls->start_seq_no + FFMIN(c->live_start_index,
pls->n_segments - 1);
/* If #EXT-X-START in playlist, need to recalculate */
if (pls->time_offset_flag && c->prefer_x_start) {
int64_t start_timestamp;
int64_t playlist_duration = 0;
int64_t cur_timestamp = c->cur_timestamp == AV_NOPTS_VALUE ? 0 :
c->cur_timestamp;
for (int i = 0; i < pls->n_segments; i++)
playlist_duration += pls->segments[i]->duration;
/* If the absolute value of TIME-OFFSET exceeds
* the duration of the playlist, it indicates either the end of the
* playlist (if positive) or the beginning of the playlist (if
* negative). */
if (pls->start_time_offset >=0 &&
pls->start_time_offset > playlist_duration)
start_timestamp = cur_timestamp + playlist_duration;
else if (pls->start_time_offset >= 0 &&
pls->start_time_offset <= playlist_duration)
start_timestamp = cur_timestamp + pls->start_time_offset;
else if (pls->start_time_offset < 0 &&
pls->start_time_offset < -playlist_duration)
start_timestamp = cur_timestamp;
else if (pls->start_time_offset < 0 &&
pls->start_time_offset > -playlist_duration)
start_timestamp = cur_timestamp + playlist_duration +
pls->start_time_offset;
else
start_timestamp = cur_timestamp;
find_timestamp_in_playlist(c, pls, start_timestamp, &seq_no, NULL);
}
return seq_no;
}
/* Otherwise just start on the first segment. */
@ -2476,6 +2530,8 @@ static int hls_probe(const AVProbeData *p)
static const AVOption hls_options[] = {
{"live_start_index", "segment index to start live streams at (negative values are from the end)",
OFFSET(live_start_index), AV_OPT_TYPE_INT, {.i64 = -3}, INT_MIN, INT_MAX, FLAGS},
{"prefer_x_start", "prefer to use #EXT-X-START if it's in playlist instead of live_start_index",
OFFSET(prefer_x_start), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS},
{"allowed_extensions", "List of file extensions that hls is allowed to access",
OFFSET(allowed_extensions), AV_OPT_TYPE_STRING,
{.str = "3gp,aac,avi,ac3,eac3,flac,mkv,m3u8,m4a,m4s,m4v,mpg,mov,mp2,mp3,mp4,mpeg,mpegts,ogg,ogv,oga,ts,vob,wav"},