[FFmpeg-devel] [PATCH] libavformat/mov.c: fix seek issues for fragmented mp4 files

[Srikanth Kotagiri]

please ignore this patch. I will submit a corrected one.

On Mon, Jan 27, 2025 at 5:20 PM Srikanth Kiran Kotagiri
<srikanthk at gmail.com> wrote:
>
> For Fragmented MP4 files where the audio and video streams are written to seperate fragments, the -ss option will cause the file pointer to be set to the first available fragment. This is due to an interaction in search_frag_timestamp() function and get_frag_time() functions.
>
> With this change, we first verify that the fragment does not actually contain the requested fragment before just sending AV_NOPTS_VALUE.
> ---
>  libavformat/mov.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index c016ce8e41..f3e4f4deff 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -87,6 +87,7 @@ typedef struct MOVParseTableEntry {
>  static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom);
>  static int mov_read_mfra(MOVContext *c, AVIOContext *f);
>  static void mov_free_stream_context(AVFormatContext *s, AVStream *st);
> +static int mov_switch_root(AVFormatContext *s, int64_t target, int index);
>
>  static int mov_metadata_track_or_disc_number(MOVContext *c, AVIOContext *pb,
>                                               unsigned len, const char *key)
> @@ -1680,6 +1681,27 @@ static int64_t get_frag_time(AVFormatContext *s, AVStream *dst_st,
>          return frag_stream_info->sidx_pts;
>      }
>
> +
> +    // Check if the requested stream is present in the fragment
> +    int stream_present = 0;
> +    for (i = 0; i < frag_index->item[index].nb_stream_info; i++) {
> +        if (dst_st->id != frag_index->item[index].stream_info[i].id)
> +            continue;
> +        if ( get_stream_info_time(&frag_index->item[index].stream_info[i]) != AV_NOPTS_VALUE) {
> +            exists = 1;
> +            break;
> +        }
> +        if ( mov_switch_root(s,-1,index) < 0)
> +            return AV_NOPTS_VALUE;
> +        if ( get_stream_info_time(&frag_index->item[index].stream_info[i]) != AV_NOPTS_VALUE) {
> +            exists = 1;
> +            break;
> +        }
> +    }
> +    if (!stream_present)
> +        return AV_NOPTS_VALUE;
> +
> +
>      for (i = 0; i < frag_index->item[index].nb_stream_info; i++) {
>          AVStream *frag_stream = NULL;
>          frag_stream_info = &frag_index->item[index].stream_info[i];
> --
> 2.39.5 (Apple Git-154)
>