[FFmpeg-devel] [PATCH 1/1] avformat/dashenc: Added #EXT-X-PROGRAM-DATE-TIME to HLS playlists

[Jeyapal, Karthick]

On 2/22/19 12:25 PM, joepadmiraal wrote:
> From: joepadmiraal <joep at groovytunes.nl>
>
> ---
>  libavformat/dashenc.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
> index 37a7547b12..d0d0d6f030 100644
> --- a/libavformat/dashenc.c
> +++ b/libavformat/dashenc.c
> @@ -122,6 +122,7 @@ typedef struct DASHContext {
>      int64_t last_duration;
>      int64_t total_duration;
>      char availability_start_time[100];
> +    int64_t start_time_ms;
>      char dirname[1024];
>      const char *single_file_name;  /* file names as specified in options */
>      const char *init_seg_name;
> @@ -432,6 +433,8 @@ static void write_hls_media_playlist(OutputStream *os, AVFormatContext *s,
>      const char *proto = avio_find_protocol_name(c->dirname);
>      int use_rename = proto && !strcmp(proto, "file");
>      int i, start_index, start_number;
> +    time_t start_time_s = c->start_time_ms / 1000;
> +    double prog_date_time = start_time_s;
>  
>      get_start_index_number(os, c, &start_index, &start_number);
>  
> @@ -464,16 +467,21 @@ static void write_hls_media_playlist(OutputStream *os, AVFormatContext *s,
>      ff_hls_write_init_file(c->m3u8_out, os->initfile, c->single_file,
>                             os->init_range_length, os->init_start_pos);
>  
> -    for (i = start_index; i < os->nb_segments; i++) {
> +    for (i = 0; i < os->nb_segments; i++) {
>          Segment *seg = os->segments[i];
> -        ret = ff_hls_write_file_entry(c->m3u8_out, 0, c->single_file,
> -                                (double) seg->duration / timescale, 0,
> -                                seg->range_length, seg->start_pos, NULL,
> -                                c->single_file ? os->initfile : seg->file,
> -                                NULL);
> -        if (ret < 0) {
> -            av_log(os->ctx, AV_LOG_WARNING, "ff_hls_write_file_entry get error\n");
> +        double duration = (double) seg->duration / timescale;
> +        if (i >= start_index) {
> +            double prog_date_time_copy = prog_date_time;
> +            ret = ff_hls_write_file_entry(c->m3u8_out, 0, c->single_file,
> +                                    duration, 0,
> +                                    seg->range_length, seg->start_pos, NULL,
> +                                    c->single_file ? os->initfile : seg->file,
> +                                    &prog_date_time_copy);
> +            if (ret < 0) {
> +                av_log(os->ctx, AV_LOG_WARNING, "ff_hls_write_file_entry get error\n");
> +            }
>          }
> +        prog_date_time += duration;
Hi Joep,

It is great to see that you are submitting your changes back to the community for improving dashenc features.
Really appreciate your effort on this. Thank you very much.

In terms for the actual changes, I have review comment. The algorithmic complexity for calculating prog_date_time will increase with the time software has been running continuously. For example, if the software has been running for seven days continuously (with window_size parameter enabled for a live input), it will take smaller cpu time to compute prog_date_time on the first day, and much longer time on the seventh day. Such kind of algorithms affect the stability of the software in long-duration runs for live input. Could you please modify the algorithm so that the prog_date_time calculation's complexity doesn't increase linearly with time.

Regards,
Karthick
>      }
>  
>      if (prefetch_url)
> @@ -1583,9 +1591,12 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
>          os->first_pts = pkt->pts;
>      os->last_pts = pkt->pts;
>  
> -    if (!c->availability_start_time[0])
> +    if (!c->availability_start_time[0]) {
> +        int64_t start_time_us = av_gettime();
> +        c->start_time_ms = start_time_us / 1000;
>          format_date_now(c->availability_start_time,
>                          sizeof(c->availability_start_time));
> +    }
>  
>      if (!os->availability_time_offset && pkt->duration) {
>          int64_t frame_duration = av_rescale_q(pkt->duration, st->time_base,