[FFmpeg-devel] [PATCH] avformat/hls:use EXT-X-START instead of live_start_index if it's in playlist
Steven Liu
lq at chinaffmpeg.org
Sat Jun 25 07:51:15 EEST 2022
> 在 2022年6月25日，12:32，少宇李 <wolfleekay at gmail.com> 写道：
>
> Hi Steven,
>
> Please review code.
>
> I changed code, but I still have a question.
> If EXT-X-START tag in playlist and users set live_start_index, the
> live_start_index will not work
> for current codes, which makes maybe users confused.
> Is that OK?
for current codes, user cannot aware there have EXT-X-START tag in the playlist, so i think we should reserve the old use method.
or maybe you can add an option for user to decide which way they can use (either EXT-X-START or live_start_index).
Because there should have many people using live_start_index for 'time shift’ by player (user control),
>
> In other hand, if make live_start_index valid when EXT-X-START tag in
> playlist, maybe live_start_index needs a flag, or
> make live_start_index default value is INT_MIN to distinguish.
> becuase the live_start_index default value is -3, I have no idea to
> distinguish users action or
> default value when live_start_index=-3.
yes cannot distinguish users action, but user should can decided use live_start_index or EXT-X-START.
>
> May I need to set default value=INT_MIN as live_start_index default value?
> And only when does not exist EXT-X-START
> tag in playlist, make live_start_index = -3 or users's configuration value.
> I have no idea which is better~
>
> Thanks a lot!
>
> Steven Liu <lingjiujianke at gmail.com> 于2022年6月24日周五 14:21写道：
>
>> 少宇李 <wolfleekay at gmail.com> 于2022年6月24日周五 11:58写道：
>>>>
>>>>
>>>> Hi, Steven
>>>
>>>
>>> I got it.
>>>
>>> User could use "live_start_index" option even if #EXT-X-START in the
>> playlist.
>>>
>>> I changed the priority about #EXT-X-START/live_start_index,
>>>
>>> this is new bellow:
>>>
>>> ---
>>> libavformat/hls.c | 69 +++++++++++++++++++++++++++++++++++++++++++----
>>> 1 file changed, 64 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/libavformat/hls.c b/libavformat/hls.c
>>> index b736f093a9..309471efce 100644
>>> --- a/libavformat/hls.c
>>> +++ b/libavformat/hls.c
>>> @@ -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;
>>> @@ -741,6 +743,7 @@ static int parse_playlist(HLSContext *c, const char
>> *url,
>>> struct segment **prev_segments = NULL;
>>> int prev_n_segments = 0;
>>> int64_t prev_start_seq_no = -1;
>>> + const char *p;
>>>
>>> if (is_http && !in && c->http_persistent && c->playlist_pb) {
>>> in = c->playlist_pb;
>>> @@ -889,6 +892,18 @@ static int parse_playlist(HLSContext *c, const char
>> *url,
>>> cur_init_section->key = NULL;
>>> }
>>>
>>> + } else if (av_strstart(line, "#EXT-X-START:", &ptr)) {
>>> + ret = ensure_playlist(c, &pls, url);
>>> + if (ret < 0) {
>>> + goto fail;
>>> + }
>>> + if (av_strstart(ptr, "TIME-OFFSET=", &p)) {
>>> + float offset = strtof(p, NULL);
>>> + pls->start_time_offset = offset * AV_TIME_BASE;
>>> + pls->time_offset_flag = 1;
>>> + } else {
>>> + goto fail;
>>> + }
>>> } else if (av_strstart(line, "#EXT-X-ENDLIST", &ptr)) {
>>> if (pls)
>>> pls->finished = 1;
>>> @@ -1721,10 +1736,54 @@ 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);
>>> - else
>>> - return pls->start_seq_no + FFMIN(c->live_start_index,
>> pls->n_segments - 1);
>>> + if (c->live_start_index != INT_MIN) {
>> Maybe you should not change current logic.
>> You can just add about process EXT-X-START sence,.
>> For example:
>> compute the start_seq_no and save the value to a temp varible and
>> don't return immediately, check the third scence which get EXT-X-START
>> tag from playlist.
>> process the temp varible after start_seq_no compute from
>> live_start_index or EXT-X-START.
>>
>>> + if (c->live_start_index < 0)
>>> + return 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);
>>> + } else if (c->live_start_index == INT_MIN &&
>> !pls->time_offset_flag) {
>>> + return pls->start_seq_no + FFMAX(pls->n_segments - 3, 0);
>>> + } else {
>>> + /* If playlist indicate a TIME-OFFSET and user not use
>> live_start_index,
>>> + * need to recalculate seq_no */
>>> + int i;
>>> + int64_t start_timestamp;
>>> + int64_t playlist_duration = 0;
>>> + int64_t cur_timestamp = c->cur_timestamp == AV_NOPTS_VALUE
>> ? 0 :
>>> + c->cur_timestamp;
>>> +
>>> + for (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);
>>> + av_log(c, AV_LOG_DEBUG, "start_timestamp: %" PRId64
>>> + "cur_timestamp:%" PRId64
>>> + "cur_seq_no:%" PRId64 "\n",
>>> + start_timestamp, cur_timestamp,
>> seq_no);
>>> + return seq_no;
>>> + }
>>> }
>>>
>>> /* Otherwise just start on the first segment. */
>>> @@ -2475,7 +2534,7 @@ static int hls_probe(const AVProbeData *p)
>>> #define FLAGS AV_OPT_FLAG_DECODING_PARAM
>>> 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},
>>> + OFFSET(live_start_index), AV_OPT_TYPE_INT, {.i64 = INT_MIN},
>> INT_MIN, INT_MAX, FLAGS},
>> This is unnecessary， because the default -3 is ok and be using by
>> users from many years ago.
>>
>>> {"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"},
>>> --
>>> 2.24.1 (Apple Git-126)
>>>
>>>
>>> Thanks Steven
>>
> <0001-avformat-hls-use-EXT-X-START-instead-of-live_start_i.patch>_______________________________________________
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Thanks
Steven
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