[FFmpeg-devel] [PATCH] avformat/dashenc: Only use temporary files when outputting to file protocol

[Thomas Stephens]

Has anybody had a chance to look at this patch?

Thanks,
--Thomas

On Tue, Feb 7, 2017, 2:20 PM Thomas Stephens <thomas at ustudio.com> wrote:

> Skips using temporary files when outputting to a protocol other than
> "file", which enables dash to output content over network
> protocols. The logic has been copied from the HLS format.
> ---
>  libavformat/dashenc.c | 29 +++++++++++++++++++++++------
>  1 file changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/libavformat/dashenc.c b/libavformat/dashenc.c
> index 534fa75..fa56505 100644
> --- a/libavformat/dashenc.c
> +++ b/libavformat/dashenc.c
> @@ -444,9 +444,15 @@ static int write_manifest(AVFormatContext *s, int
> final)
>      AVIOContext *out;
>      char temp_filename[1024];
>      int ret, i;
> +    const char *proto = avio_find_protocol_name(s->filename);
> +    int use_rename = proto && !strcmp(proto, "file");
> +    static unsigned int warned_non_file = 0;
>      AVDictionaryEntry *title = av_dict_get(s->metadata, "title", NULL, 0);
>
> -    snprintf(temp_filename, sizeof(temp_filename), "%s.tmp", s->filename);
> +    if (!use_rename && !warned_non_file++)
> +        av_log(s, AV_LOG_ERROR, "Cannot use rename on non file protocol,
> this may lead to races and temporary partial files\n");
> +
> +    snprintf(temp_filename, sizeof(temp_filename), use_rename ? "%s.tmp"
> : "%s", s->filename);
>      ret = s->io_open(s, &out, temp_filename, AVIO_FLAG_WRITE, NULL);
>      if (ret < 0) {
>          av_log(s, AV_LOG_ERROR, "Unable to open %s for writing\n",
> temp_filename);
> @@ -548,7 +554,11 @@ static int write_manifest(AVFormatContext *s, int
> final)
>      avio_printf(out, "</MPD>\n");
>      avio_flush(out);
>      ff_format_io_close(s, &out);
> -    return avpriv_io_move(temp_filename, s->filename);
> +
> +    if (use_rename)
> +        return avpriv_io_move(temp_filename, s->filename);
> +
> +    return 0;
>  }
>
>  static int dash_init(AVFormatContext *s)
> @@ -796,6 +806,10 @@ static int dash_flush(AVFormatContext *s, int final,
> int stream)
>  {
>      DASHContext *c = s->priv_data;
>      int i, ret = 0;
> +
> +    const char *proto = avio_find_protocol_name(s->filename);
> +    int use_rename = proto && !strcmp(proto, "file");
> +
>      int cur_flush_segment_index = 0;
>      if (stream >= 0)
>          cur_flush_segment_index = c->streams[stream].segment_index;
> @@ -833,7 +847,7 @@ static int dash_flush(AVFormatContext *s, int final,
> int stream)
>          if (!c->single_file) {
>              dash_fill_tmpl_params(filename, sizeof(filename),
> c->media_seg_name, i, os->segment_index, os->bit_rate, os->start_pts);
>              snprintf(full_path, sizeof(full_path), "%s%s", c->dirname,
> filename);
> -            snprintf(temp_path, sizeof(temp_path), "%s.tmp", full_path);
> +            snprintf(temp_path, sizeof(temp_path), use_rename ? "%s.tmp"
> : "%s", full_path);
>              ret = s->io_open(s, &os->out, temp_path, AVIO_FLAG_WRITE,
> NULL);
>              if (ret < 0)
>                  break;
> @@ -851,9 +865,12 @@ static int dash_flush(AVFormatContext *s, int final,
> int stream)
>              find_index_range(s, full_path, start_pos, &index_length);
>          } else {
>              ff_format_io_close(s, &os->out);
> -            ret = avpriv_io_move(temp_path, full_path);
> -            if (ret < 0)
> -                break;
> +
> +            if (use_rename) {
> +                ret = avpriv_io_move(temp_path, full_path);
> +                if (ret < 0)
> +                    break;
> +            }
>          }
>          add_segment(os, filename, os->start_pts, os->max_pts -
> os->start_pts, start_pos, range_length, index_length);
>          av_log(s, AV_LOG_VERBOSE, "Representation %d media segment %d
> written to: %s\n", i, os->segment_index, full_path);
> --
> 2.5.0
>
>