Re: [FFmpeg-devel] [PATCH v2 1/2] avformat: add avformat_query_seekable

[Stefano Sabatini <stefasab@gmail.com>]

On date Tuesday 2025-04-22 10:24:01 +0530, Gyan Doshi wrote:
> On 2025-04-21 11:59 pm, Stefano Sabatini wrote:
> > On date Tuesday 2025-04-15 16:09:56 +0530, Gyan Doshi wrote:
> > > Utility function to report seekability features for a given input.
> > > 
> > > Useful for ffprobe and to extend seek possibilities in fftools.
> > > ---
> > > v2:
> > >     made constants more descriptive
> > >     add exception for rtsp false negative seekability
> > > 
> > >   doc/APIchanges         |  3 +++
> > >   libavformat/avformat.h | 22 ++++++++++++++++++
> > >   libavformat/seek.c     | 53 ++++++++++++++++++++++++++++++++++++++++++
> > >   libavformat/version.h  |  2 +-
> > >   4 files changed, 79 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/doc/APIchanges b/doc/APIchanges
> > > index 65bf5a9419..879f56b572 100644
> > > --- a/doc/APIchanges
> > > +++ b/doc/APIchanges
> > > @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2025-03-28
> > >   API changes, most recent first:
> > > +2025-04-xx - xxxxxxxxxx - lavf 62.1.100 - avformat.h
> > > +  Add avformat_query_seekable().
> > > +
> > >   2025-04-07 - 19e9a203b7 - lavu 60.01.100 - dict.h
> > >     Add AV_DICT_DEDUP.
> > > diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> > > index 498c3020a5..f9da5e9e79 100644
> > > --- a/libavformat/avformat.h
> > > +++ b/libavformat/avformat.h
> > > @@ -2338,6 +2338,28 @@ int av_seek_frame(AVFormatContext *s, int stream_index, int64_t timestamp,
> > >    */
> > >   int avformat_seek_file(AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
> > > +#define AVSEEKABLE_IO_NORMAL       0x00000001 ///< I/O is seekable like a local file
> > > +#define AVSEEKABLE_IO_PROTOCOL     0x00000002 ///< I/O seek is through protocol request via avio_seek_time
> > > +#define AVSEEKABLE_VIA_DEMUXER     0x00000004 ///< demuxer has a seek function
> > > +#define AVSEEKABLE_VIA_PKTSCAN     0x00000008 ///< seek is performed by consuming and scanning packet timestamps
> > > +#define AVSEEKABLE_BY_TIME         0x00000100 ///< seek target can be a timestamp
> > > +#define AVSEEKABLE_BY_BYTE         0x00000200 ///< seek target can be in bytes
> > > +#define AVSEEKABLE_BY_FRAME        0x00000400 ///< seek target can be a frame index
> > > +#define AVSEEKABLE_PROP_PTS        0x00010000 ///< seek target timestamp is expected to be PTS
> > > +#define AVSEEKABLE_PROP_FAST       0x00020000 ///< demuxer allows fast but inaccurate seeking

> > > +#define AVSEEKABLE_PROP_FWDONLY    0x00040000 ///< set seek will be equal or forward of specified seek point
> > Not sure I get this, can you clarify/expand?
> 
> The framework does not seek to an earlier KF, e.g. if either avio is not
> AVIO_SEEKABLE_NORMAL or the index does not correctly mark keyframes. then a
> seek to 12s will return frames from 12s and decoding will start from next KF
> encountered.

Thanks for the clarification. This is my take to integrate this
comment into the doxy (also it's probably best to avoid contractions
to improve mnemonics):
#define AVSEEKABLE_PROP_FORWARDONLY    0x00040000 ///< seek result position will be equal or forward of the specified seek point

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