[FFmpeg-devel] [PATCH] lavf/dashenc: Write media trailers when DASH trailer is written.

[Jeyapal, Karthick]

On 11/28/18 5:13 PM, Andrey Semashev wrote:
> This commit ensures that all (potentially, long) filesystem activity is
> performed when the user calls av_write_trailer on the DASH libavformat
> context, not when freeing the context. Also, this defers media segment
> deletion until after the media trailers are written.
> ---
>  libavformat/dashenc.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
> index 6ce70e0076..e1c959dc89 100644
> --- a/libavformat/dashenc.c
> +++ b/libavformat/dashenc.c
> @@ -424,8 +424,6 @@ static void dash_free(AVFormatContext *s)
>          return;
>      for (i = 0; i < s->nb_streams; i++) {
>          OutputStream *os = &c->streams[i];
> -        if (os->ctx && os->ctx_inited)
> -            av_write_trailer(os->ctx);
>          if (os->ctx && os->ctx->pb)
>              ffio_free_dyn_buf(&os->ctx->pb);
>          ff_format_io_close(s, &os->out);
> @@ -1420,13 +1418,11 @@ static int dash_flush(AVFormatContext *s, int final, int stream)
>          os->pos += range_length;
>      }
>  
> -    if (c->window_size || (final && c->remove_at_exit)) {
> +    if (c->window_size) {
>          for (i = 0; i < s->nb_streams; i++) {
>              OutputStream *os = &c->streams[i];
>              int j;
>              int remove = os->nb_segments - c->window_size - c->extra_window_size;
> -            if (final && c->remove_at_exit)
> -                remove = os->nb_segments;
Is there any reason for deferring the delete after write_trailer.
Because if the file is getting deleted immediately, why should we bother about write_trailer? Is it causing any issues?
I am asking this, because the segment deletion code is getting duplicated due to this change. I am trying to avoid code duplication as much as possible.
>              if (remove > 0) {
>                  for (j = 0; j < remove; j++) {
>                      char filename[1024];
> @@ -1599,11 +1595,24 @@ static int dash_write_trailer(AVFormatContext *s)
>      }
>      dash_flush(s, 1, -1);
>  
> +    for (int i = 0; i < s->nb_streams; ++i) {
Can we merge this loop with the below loop for deleting init segments. The "if" condition for remove_at_exit, could be moved inside the merged loop. 
> +        OutputStream *os = &c->streams[i];
> +        if (os->ctx && os->ctx_inited) {
> +            av_write_trailer(os->ctx);
> +        }
> +    }
> +
>      if (c->remove_at_exit) {
>          char filename[1024];
>          int i;
>          for (i = 0; i < s->nb_streams; i++) {
>              OutputStream *os = &c->streams[i];
> +            for (int j = 0; j < os->nb_segments; ++j) {
> +                snprintf(filename, sizeof(filename), "%s%s", c->dirname, os->segments[j]->file);
> +                dashenc_delete_file(s, filename);
> +                av_free(os->segments[j]);
> +            }
> +            os->nb_segments = 0;
>              snprintf(filename, sizeof(filename), "%s%s", c->dirname, os->initfile);
>              dashenc_delete_file(s, filename);
>          }