[FFmpeg-devel] [PATCH] avformat/concatdec: don't call open_file when seek position within a file

[Nicolas George]

Le jour de la Récompense, an CCXXIV, raymond a écrit :
> ---
>  libavformat/concatdec.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)

Thanks for the patch. The object of the change is interesting, but there are
some implementation concerns, see below.

Also, remember that top-posting is not accepted on this list; if you do not
know what it means, look it up.

> 
> diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
> index b3a430e..1cd9ec1 100644
> --- a/libavformat/concatdec.c
> +++ b/libavformat/concatdec.c
> @@ -64,6 +64,8 @@ typedef struct {
>      ConcatMatchMode stream_match_mode;
>      unsigned auto_convert;
>      int segment_time_metadata;

> +    int cur_fileno;

This information is already available as "cur_file - files", see
open_next_file() for example. There is no need for an extra variable.

> +    AVFormatContext *cur_avf_saved;

This variable serves only locally for concat_seek() and real_seek(), it
would be better as just a parameter to real_seek().

>  } ConcatContext;
>  
>  static int concat_probe(AVProbeData *probe)
> @@ -333,6 +335,8 @@ static int open_file(AVFormatContext *avf, unsigned fileno)
>          avformat_close_input(&cat->avf);
>          return ret;
>      }
> +
> +    cat->cur_fileno = fileno;
>      cat->cur_file = file;
>      if (file->start_time == AV_NOPTS_VALUE)
>          file->start_time = !fileno ? 0 :
> @@ -711,13 +715,18 @@ static int real_seek(AVFormatContext *avf, int stream,
>              left  = mid;
>      }
>  
> -    if ((ret = open_file(avf, left)) < 0)
> -        return ret;
> +    if (cat->cur_fileno != left) {
> +        if ((ret = open_file(avf, left)) < 0)
> +            return ret;
> +    } else {
> +        cat->avf = cat->cur_avf_saved;
> +    }
>  
>      ret = try_seek(avf, stream, min_ts, ts, max_ts, flags);
>      if (ret < 0 &&
>          left < cat->nb_files - 1 &&
>          cat->files[left + 1].start_time < max_ts) {

> +        cat->avf = NULL;

This leaks if cat->avf is not cur_avf_saved, I think.

>          if ((ret = open_file(avf, left + 1)) < 0)
>              return ret;
>          ret = try_seek(avf, stream, min_ts, ts, max_ts, flags);
> @@ -730,7 +739,7 @@ static int concat_seek(AVFormatContext *avf, int stream,
>  {
>      ConcatContext *cat = avf->priv_data;
>      ConcatFile *cur_file_saved = cat->cur_file;
> -    AVFormatContext *cur_avf_saved = cat->avf;

> +    cat->cur_avf_saved = cat->avf;
>      int ret;

Interleaving statements and variables is not allowed in the code base.

>  
>      if (!cat->seekable)
> @@ -739,12 +748,16 @@ static int concat_seek(AVFormatContext *avf, int stream,
>          return AVERROR(ENOSYS);
>      cat->avf = NULL;
>      if ((ret = real_seek(avf, stream, min_ts, ts, max_ts, flags)) < 0) {
> -        if (cat->avf)
> -            avformat_close_input(&cat->avf);
> -        cat->avf      = cur_avf_saved;
> +        if (cat->cur_file != cur_file_saved) {
> +            if (cat->avf)
> +                avformat_close_input(&cat->avf);
> +        }
> +        cat->avf      = cat->cur_avf_saved;
>          cat->cur_file = cur_file_saved;
>      } else {
> -        avformat_close_input(&cur_avf_saved);
> +        if (cat->cur_file != cur_file_saved) {
> +            avformat_close_input(&cat->cur_avf_saved);
> +        }
>          cat->eof = 0;
>      }
>      return ret;

Regards,

-- 
  Nicolas George
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