[FFmpeg-devel] [PATCH v1] avformat/hlsenc: fix hls_time not respected

[Gyan Doshi]

On 2025-01-24 05:29 pm, Ingo Oppermann wrote:
> This fixes the criterion when to split the segments based on the elapsed time
> for the current segment instead of using the theoretical elapsed time since
> start based on hls_time and the number of written segments.
>
> hls_time is used to define the minimum 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. 40 seconds.
> After that, key frames will come every second. This will result in segments
> that are first 10 seconds, then 1 second for some time and later 2 seconds as
> expected.

Better to make it flexible like how the segment muxer does it, by having 
an optional minimum segment duration parameter. Then it's upto the user.
See d39b34123d.

Also Patchwork warns about the line length in the commit message. Should 
be <=72

Regards,
Gyan


>
> How to reproduce:
> ffmpeg -t 40 -f lavfi -i testsrc2=s=1280x720:r=25 -codec:v libx264 -g 250 part1.mp4
> ffmpeg -t 40 -f lavfi -i testsrc2=s=1280x720:r=25 -codec:v libx264 -g 25 part2.mp4
> echo "file part1.mp4\nfile part2.mp4" > list.txt
> ffmpeg -f concat -i list.txt -codec copy part.mp4
> ffmpeg -i part.mp4 -codec copy -f hls -hls_time 2 -hls_list_size 0 -hls_segment_filename 'part_%d.ts' part.m3u8
> cat part.m3u8
>
> Signed-off-by: Ingo Oppermann <ingo at datarhei.com>
> ---
>   libavformat/hlsenc.c | 12 +++---------
>   1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
> index 6148685f40..2c5d60500d 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -2474,7 +2474,6 @@ 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;
>       int is_ref_pkt = 1;
>       int ret = 0, can_split = 1, i, j;
>       int stream_index = 0;
> @@ -2512,14 +2511,9 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
>           return AVERROR(ENOMEM);
>       }
>   
> -    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;
> +        /* reset hls->recording_time at end of the init hls list */
>           hls->recording_time = hls->time;
> -        end_pts = init_list_dur + after_init_list_dur ;
>       }
>   
>       if (vs->start_pts == AV_NOPTS_VALUE) {
> @@ -2560,8 +2554,8 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
>       }
>   
>       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,
> -                                                          end_pts, AV_TIME_BASE_Q) >= 0) {
> +    if (vs->packets_written && can_split && av_compare_ts(pkt->pts - vs->end_pts, st->time_base,
> +                                                          hls->recording_time, AV_TIME_BASE_Q) >= 0) {
>           int64_t new_start_pos;
>           int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);
>           double cur_duration;
>
> base-commit: e20ee9f9aec94f8cea1bf4fd8ed3fb096fb205e5