[FFmpeg-devel] [PATCH v2] avformat/hlsenc: add hls_min_time to guarantee minimal segment duration
Steven Liu
lingjiujianke at gmail.com
Thu Jun 5 10:34:41 EEST 2025
Ingo Oppermann <ingo at datarhei.com> 于2025年6月5日周四 15:24写道：
>
> The current implementation of the hls_time might produce segments
> with shorter duration in some cases which is not as expected. With the
> hls_min_time option the minimal segment duration will be guaranteed by
> splitting by the next keyframe after the desired duration of the
> segment has been reached.
>
> Instead of changing the current behaviour of hls_time which might
> break existing workflows, the new option hls_min_time will override
> hls_time and guarantee the minimal segment duration.
>
> hls_time is supposed to define the minimal length of a segment,
> however this is not respected in all cases when a stream has variable
> GOP sizes.
>
> Imagine a stream starts with a key frame every 10 seconds for
> e.g. 30 seconds. After that, key frames will come every second. This
> will result in segments that are first 10 seconds (as expected), then
> 1 second for some time (not as expected) and later 2 seconds (as
> expected).
>
> How to reproduce:
> ffmpeg -t 30 -f lavfi -i testsrc2 -codec:v libx264 -g 250 part1.mp4
> ffmpeg -t 30 -f lavfi -i testsrc2 -codec:v libx264 -g 25 part2.mp4
> echo "file part1.mp4\nfile part2.mp4" > list.txt
> ffmpeg -f concat -i list.txt -codec copy \
> -f hls -hls_time 2 -hls_list_size 0 parts.m3u8
> cat parts.m3u8
>
> v2 changes:
> Adjusting wording in commit message as suggested by Steven Liu.
>
> Signed-off-by: Ingo Oppermann <ingo at datarhei.com>
> ---
> doc/muxers.texi | 7 +++++++
> libavformat/hlsenc.c | 27 ++++++++++++++++++++-------
> 2 files changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/doc/muxers.texi b/doc/muxers.texi
> index 30c95c3d34..082647bd9d 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -1929,6 +1929,13 @@ Set the target segment length. Default value is 2.
> see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
> Segment will be cut on the next key frame after this time has passed.
>
> + at item hls_min_time @var{duration}
> +Set the minimum target segment length. Default value is 0.
> +
> + at var{duration} must be a time duration specification,
> +see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
> +Segment will be at least this long and will be cut at the following key frame. If set, it will override @option{hls_time}.
> +
> @item hls_list_size @var{size}
> Set the maximum number of playlist entries. If set to 0 the list file
> will contain all the segments. Default value is 5.
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index a93d35ab75..082229467f 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -204,6 +204,7 @@ typedef struct HLSContext {
> uint32_t start_sequence_source_type; // enum StartSequenceSourceType
>
> int64_t time; // Set by a private option.
> + int64_t min_time; // Set by a private option.
> int64_t init_time; // Set by a private option.
> int max_nb_segments; // Set by a private option.
> int hls_delete_threshold; // Set by a private option.
> @@ -2506,7 +2507,7 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
> HLSContext *hls = s->priv_data;
> AVFormatContext *oc = NULL;
> AVStream *st = s->streams[pkt->stream_index];
> - int64_t end_pts = 0;
> + int64_t end_pts = 0, current_pts;
> int is_ref_pkt = 1;
> int ret = 0, can_split = 1, i, j;
> int stream_index = 0;
> @@ -2547,11 +2548,16 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
> end_pts = hls->recording_time * vs->number;
>
> if (vs->sequence - vs->nb_entries > hls->start_sequence && hls->init_time > 0) {
> - /* reset end_pts, hls->recording_time at end of the init hls list */
> - int64_t init_list_dur = hls->init_time * vs->nb_entries;
> - int64_t after_init_list_dur = (vs->sequence - hls->start_sequence - vs->nb_entries) * hls->time;
> - hls->recording_time = hls->time;
> - end_pts = init_list_dur + after_init_list_dur ;
> + if (hls->min_time > 0) {
> + hls->recording_time = hls->min_time;
> + hls->init_time = 0;
> + } else {
> + /* reset end_pts, hls->recording_time at end of the init hls list */
> + int64_t init_list_dur = hls->init_time * vs->nb_entries;
> + int64_t after_init_list_dur = (vs->sequence - hls->start_sequence - vs->nb_entries) * hls->time;
> + hls->recording_time = hls->time;
> + end_pts = init_list_dur + after_init_list_dur;
> + }
> }
>
> if (vs->start_pts == AV_NOPTS_VALUE) {
> @@ -2591,8 +2597,14 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
> }
> }
>
> + current_pts = pkt->pts - vs->start_pts;
> + if (hls->min_time > 0 && hls->init_time == 0) {
> + current_pts = pkt->pts - vs->end_pts;
> + end_pts = hls->min_time;
> + }
> +
> can_split = can_split && (pkt->pts - vs->end_pts > 0);
> - if (vs->packets_written && can_split && av_compare_ts(pkt->pts - vs->start_pts, st->time_base,
> + if (vs->packets_written && can_split && av_compare_ts(current_pts, st->time_base,
> end_pts, AV_TIME_BASE_Q) >= 0) {
> int64_t new_start_pos;
> int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);
> @@ -3214,6 +3226,7 @@ static int hls_init(AVFormatContext *s)
> static const AVOption options[] = {
> {"start_number", "set first number in the sequence", OFFSET(start_sequence),AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, E},
> {"hls_time", "set segment length", OFFSET(time), AV_OPT_TYPE_DURATION, {.i64 = 2000000}, 0, INT64_MAX, E},
> + {"hls_min_time", "set minimum segment length", OFFSET(min_time), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, E},
> {"hls_init_time", "set segment length at init list", OFFSET(init_time), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, E},
> {"hls_list_size", "set maximum number of playlist entries", OFFSET(max_nb_segments), AV_OPT_TYPE_INT, {.i64 = 5}, 0, INT_MAX, E},
> {"hls_delete_threshold", "set number of unreferenced segments to keep before deleting", OFFSET(hls_delete_threshold), AV_OPT_TYPE_INT, {.i64 = 1}, 1, INT_MAX, E},
>
> base-commit: a4c1a5b08409cdfeb8e7f92c7fd443c8ff42e00d
> --
> 2.39.5 (Apple Git-154)
>
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looks ok to me, this need a fate test case.
Thanks
Steven
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