[FFmpeg-devel] add AVSEEK_FLAG_FRAME

Michael Niedermayer michaelni
Sun Aug 16 16:58:21 CEST 2009

On Sun, Aug 16, 2009 at 03:31:02PM +0200, Ivan Schreter wrote:
> Michael Niedermayer wrote:
>> On Sat, Aug 15, 2009 at 02:33:36PM +0200, Ivan Schreter wrote:
>>   [...]
>>> Maybe a generic implementation by computing a timestamp based on frame 
>>> rate would be appropriate in avformat_seek_file?
>> doesnt work, we need the filepos based seeking for formats like MPEG-PS/TS
>> that have timestamp discontinuities and thus no reliable seeking per
>> timestamp (one of course can seek based on guessing about the 
>> discontinuities
>> but filepos is the well defined alternative if the user dislikes our, to 
>> be
>> implemented guessing)
> Uhm, but current seeking implementation for timestamp seeking for 
> MPEG-PS/TS also doesn't cope with timestamp discontinuities at all, as it's 
> not possible to seek by timestamp or frame reliably as long as there are 
> discontinuities. So I don't see this as a problem. Using timestamp = frame 
> * frame_rate / time_base would be the generic solution, so not every format 
> parser has to implement it's own solution how to position based on frames. 
> Someone just has to put an if condition and the above formula to 
> avformat_seek_file.

yes, sorry, i mixed filepos and frame num up somewhere
my reply thus was about why convertig filepos -> timestamp is not a good idea
not why frame num -> timestamp would be ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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