Re: [FFmpeg-devel] [PATCH] avformat/hls:use EXT-X-START instead of live_start_index if it's in playlist

[Li Kai <wolfleekay@gmail.com>]

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Ok, I add allowed_x_start option, and the option default is 0. So current
users will not be affected.
please review again.

At last, Thanks your tips.

Steven Liu <lq@chinaffmpeg.org> 于2022年6月25日周六 12:51写道：

>
>
> > 在 2022年6月25日，12:32，少宇李 <wolfleekay@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@gmail.com> 于2022年6月24日周五 14:21写道：
> >
> >> 少宇李 <wolfleekay@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>_______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
> Thanks
> Steven
>
>
>
>
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From 705aadf7656c65dbac999f1f2e76898c37f11321 Mon Sep 17 00:00:00 2001
From: Li Kai <wolflikai@163.com>
Date: Thu, 23 Jun 2022 00:55:38 +0800
Subject: [PATCH v2] avformat/hls: add #EXT-X-START tag support by
 allowed_x_start opt

Signed-off-by: Li Kai <wolfleekay@gmail.com>
---
 libavformat/hls.c | 58 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/libavformat/hls.c b/libavformat/hls.c
index 8204f55df3..d0daadac7c 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;
@@ -211,6 +213,7 @@ typedef struct HLSContext {
     int64_t cur_seq_no;
     int m3u8_hold_counters;
     int live_start_index;
+    int allowed_x_start;
     int first_packet;
     int64_t first_timestamp;
     int64_t cur_timestamp;
@@ -741,6 +744,7 @@ 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 +893,18 @@ 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;
@@ -1722,9 +1738,45 @@ 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->allowed_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 +2528,8 @@ 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},
+    {"allowed_x_start", "allow to use #EXT-X-START if it's in playlist instead of live_start_index",
+        OFFSET(allowed_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"},
-- 
2.25.1


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