On 2025-04-13 09:39 pm, softworkz . wrote:
-----Original Message-----
From: ffmpeg-devel<ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Gyan
Doshi
Sent: Sonntag, 13. April 2025 13:16
To:ffmpeg-devel@ffmpeg.org
Subject: [FFmpeg-devel] [PATCH 1/2] avformat: add
avformat_query_seekable
Utility function to report seekability features for a given input.
Useful for ffprobe and to extend seek possibilities in fftools.
---
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..e00f1ed0d9 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);
Hi Gyan,
I like the idea of showing seekability in FFprobe output!
As far as I understand, these flags are expressing three different things:
1. Seek method
+#define AVSEEKABLE_NORMAL 0x01 ///< I/O is seekable like a local
file
+#define AVSEEKABLE_PROTOCOL 0x02 ///< I/O seek is through protocol
request via avio_seek_time
+#define AVSEEKABLE_DEMUXER 0x04 ///< demuxer has a seek function
+#define AVSEEKABLE_PKTSCAN 0x08 ///< seek is performed by consuming
The first is not a method. It indicates whether the input is streamed.
2. Seek parameter type
and scanning packet timestamps
+#define AVSEEKABLE_TIME 0x10 ///< seek target can be a timestamp
+#define AVSEEKABLE_BYTE 0x20 ///< seek target can be in bytes
+#define AVSEEKABLE_FRAME 0x40 ///< seek target can be a frame
index
3. Additional seek behavior
+#define AVSEEKABLE_PTS 0x100 ///< seek target timestamp is
expected to be PTS
+#define AVSEEKABLE_FAST 0x200 ///< demuxer allows fast but
inaccurate seeking
+#define AVSEEKABLE_FWDONLY 0x400 ///< set seek will be equal or
forward of specified seek point
Wouldn't it be better for clarity when this differentiation would be
reflected in the naming?
Maybe something like this:
AVSEEKABLE_VIA_DEMUXER
AVSEEKABLE_BY_TIME
AVSEEKABLE_BEHAVIOR_FAST
Will do.
Another note:
+#define AVSEEKABLE_NORMAL 0x01 ///< I/O is seekable like a local
+#define AVSEEKABLE_PROTOCOL 0x02 ///< I/O seek is through protocol
+#define AVSEEKABLE_DEMUXER 0x04 ///< demuxer has a seek function
+#define AVSEEKABLE_PKTSCAN 0x08 ///< seek is performed by consuming
There's no (numeric) room for extending the first block
At the moment, there are 21 unused bits so there's no need as such.
+#define AVSEEKABLE_TIME 0x10 ///< seek target can be a timestamp
+#define AVSEEKABLE_BYTE 0x20 ///< seek target can be in bytes
+#define AVSEEKABLE_FRAME 0x40 ///< seek target can be a frame
+ // TODO: no flag for frame seeking. Add flag and update this check
+ if (s->iformat->flags & 0)
+ ret |= AVSEEKABLE_FRAME;
+
+ if (s->iformat->flags & AVFMT_SEEK_TO_PTS)
+ ret |= AVSEEKABLE_PTS;
Maybe add a check for AVSEEKABLE_TIME - for sanity?
Only a handful of demuxers have this flag, and all have TS.
This is a job for reviewers when adding the flag.
+ // TODO: flag exists but not added to the demuxers which support it
+ if (s->iformat->flags & AVFMT_FLAG_FAST_SEEK)
+ ret |= AVSEEKABLE_FAST;
Another idea would be to return a struct (like AVSeekability) with a clear
separation of those three types of information, maybe that would provide
better clarity?
As alluded above, there's only a handful of attributes being indicated.
I'd rather not spawn a new type when an inbuilt simple storage type will do.
Regards,
Gyan
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