[FFmpeg-devel] [PATCH] avformat/smacker: Support seeking to first frame

[Andreas Rheinhardt]

Andreas Rheinhardt:
> From: Timotej Lazar <timotej.lazar at araneo.si>
> 
> Add .read_seek function to the smacker demuxer for the special case of
> seeking to ts=0. This is useful because smacker – like bink, with a
> similar implementation – was mostly used to encode clips in video
> games, where random seeks are rare but looping media are common.
> 
> Signed-off-by: Timotej Lazar <timotej.lazar at araneo.si>
> ---
>  libavformat/smacker.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/libavformat/smacker.c b/libavformat/smacker.c
> index 0ca5a87b8f..5507e7c169 100644
> --- a/libavformat/smacker.c
> +++ b/libavformat/smacker.c
> @@ -349,6 +349,31 @@ next_frame:
>      return ret;
>  }
>  
> +static int smacker_read_seek(AVFormatContext *s, int stream_index,
> +                             int64_t timestamp, int flags)
> +{
> +    SmackerContext *smk = s->priv_data;
> +    int64_t ret;
> +
> +    /* only rewinding to start is supported */
> +    if (timestamp != 0) {
> +        av_log(s, AV_LOG_ERROR,
> +               "Random seeks are not supported (can only seek to start).\n");
> +        return AVERROR(EINVAL);
> +    }
> +
> +    if ((ret = avio_seek(s->pb, s->internal->data_offset, SEEK_SET)) < 0)
> +        return ret;
> +
> +    smk->cur_frame = 0;
> +    smk->next_audio_index = 0;
> +    smk->new_palette = 0;
> +    memset(smk->pal, 0, sizeof(smk->pal));
> +    memset(smk->aud_pts, 0, sizeof(smk->aud_pts));
> +
> +    return 0;
> +}
> +
>  AVInputFormat ff_smacker_demuxer = {
>      .name           = "smk",
>      .long_name      = NULL_IF_CONFIG_SMALL("Smacker"),
> @@ -356,4 +381,5 @@ AVInputFormat ff_smacker_demuxer = {
>      .read_probe     = smacker_probe,
>      .read_header    = smacker_read_header,
>      .read_packet    = smacker_read_packet,
> +    .read_seek      = smacker_read_seek,
>  };
> 
Will apply this patchset tomorrow unless there are objections.

- Andreas