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?
> +/**
> + * Report if and how a seek can be performed in a given input.
I don't like the "can be performed in a given input" part, I'd use a
terminology closer to the function name: "for this format context".
Also, probably we want to specify that the method should be used after
the open operation or whatever.
> + *
> + * @param s media file handle
> + *
> + * @return 0 if no seek can be performed on input,
> + * -1 if the fmt ctx is NULL or is not an input
> + * else return AVSEEKABLE_ bitflags indicating seekability features.
> + */
> +int avformat_query_seekable(AVFormatContext *s);
> +
> /**
> * Discard all internally buffered data. This can be useful when dealing with
> * discontinuities in the byte stream. Generally works only with formats that
> diff --git a/libavformat/seek.c b/libavformat/seek.c
> index c0d94371e6..8be1bdec30 100644
> --- a/libavformat/seek.c
> +++ b/libavformat/seek.c
> @@ -712,6 +712,59 @@ int avformat_seek_file(AVFormatContext *s, int
> stream_index, int64_t min_ts,
> return ret;
> }
>
> +int avformat_query_seekable(AVFormatContext *s)
> +{
> + int ret = 0;
> +
> + if (!s || !s->iformat)
> + return -1;
> +
> + if ( strcmp(s->iformat->name, "rtsp") && (!(s->pb && s->pb->seekable) ||
> s->ctx_flags & AVFMTCTX_UNSEEKABLE) )
> + return 0;
> +
> + if (s->pb->seekable & AVIO_SEEKABLE_NORMAL)
> + ret |= AVSEEKABLE_IO_NORMAL;
> +
> + if (s->pb->seekable & AVIO_SEEKABLE_TIME)
> + ret |= AVSEEKABLE_IO_PROTOCOL;
> +
> + if (ffifmt(s->iformat)->read_seek || ffifmt(s->iformat)->read_seek2)
> + ret |= AVSEEKABLE_VIA_DEMUXER;
> +
> + if (ffifmt(s->iformat)->read_timestamp && !(s->iformat->flags &
> AVFMT_NOBINSEARCH))
> + ret |= AVSEEKABLE_VIA_PKTSCAN;
> +
> + if (!(s->iformat->flags & AVFMT_NOTIMESTAMPS))
> + ret |= AVSEEKABLE_BY_TIME;
> +
> + // TODO: incomplete, a few demuxers don't set flag but error out on byte
> seek
> + if (!(s->iformat->flags & AVFMT_NO_BYTE_SEEK))
> + ret |= AVSEEKABLE_BY_BYTE;
> +
> + // TODO: no flag for frame seeking. Add flag and enable this check
> + if (s->iformat->flags & 0)
> + ret |= AVSEEKABLE_BY_FRAME;
> +
> + if (s->iformat->flags & AVFMT_SEEK_TO_PTS)
> + ret |= AVSEEKABLE_PROP_PTS;
> +
> + // TODO: flag exists but not added to the demuxers which support it
> + if (s->iformat->flags & AVFMT_FLAG_FAST_SEEK)
> + ret |= AVSEEKABLE_PROP_FAST;
> +
> + if (!(ret & AVSEEKABLE_VIA_DEMUXER) && ret & AVSEEKABLE_VIA_PKTSCAN)
> + ret |= AVSEEKABLE_PROP_FWDONLY;
> +
> + if ( !(ret & AVSEEKABLE_VIA_DEMUXER) &&
> + !(ret & AVSEEKABLE_VIA_PKTSCAN) &&
> + !(ret & AVSEEKABLE_BY_BYTE) &&
> + !(ret & AVSEEKABLE_IO_PROTOCOL) &&
> + (s->iformat->flags & AVFMT_NOGENSEARCH) )
> + ret = 0;
> +
> + return ret;
> +}
> +
> /** Flush the frame reader. */
> void ff_read_frame_flush(AVFormatContext *s)
> {
> diff --git a/libavformat/version.h b/libavformat/version.h
> index 752aac16f7..a7c80dc564 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -31,7 +31,7 @@
>
> #include "version_major.h"
>
> -#define LIBAVFORMAT_VERSION_MINOR 0
> +#define LIBAVFORMAT_VERSION_MINOR 1
> #define LIBAVFORMAT_VERSION_MICRO 100
>
> #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
> --
> 2.49.0
>
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