[openbeos] Solution to MediaKit sync issue resolved
- From: "Solaja, Zenja" <solaja@xxxxxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Tue, 29 Jun 2004 08:21:26 +1000
Hi everyone. I dont know if this has been reported before, if not I
apologise for hogging bandwidth, but its a discovery I made last night so I
think I ought to share it with those of you who dont know. Anyone who has
used BeOS's media kit (even for watching videos) must have observed the
sound sync issue (or lack of it) when dealing with encoded audio. I've been
working on a MediaPlayer clone (for now, grander plans later) and decided to
roll up my sleves and figure out what was the issue with audio sync.
The issue seems to be with bitrate calculations, specifically, moving from
BINARY kilo bits per second (where a kilo is 1024) to DECIMAL kilo bits per
second (where a kilo is the SI quantity of 1000). When you pass the real
time to either seek or play decoders, it will perform its calculations on
BINARY kilo, when in fact it should have done the operation in DECIMAL kilo,
since time itself is decimal (bigtime_t). When you manually adjust the seek
and play times with this offset, you finally get proper audio sync.
Eg. For 128Kbps audio codec (MP3), you need to adjust your seek/play time
with 128000/(128*1024)
Anyway, my video player using native BeOS codecs is finally 100% in sync,
and I'll gladly donate it to OBOS when its done. In my software philosophy,
software ain't done until it fulfills the following 3 requirements:
- Functional (it's useless if it doesn't do what it needs to do)
- Fast (which also means responsive)
- Fun (how intuitive is it, does it frustrate the user, does is save
settings and remember window positions and directories, stuff like that)
I've got the functional and fast bits sorted out, now the difference between
a good app and a great app is how much fun it is to use. So I'll be
spending my time on the fun requirement for now.
/me crawls back under rock
Zenja Solaja
<ps - not in any way speaking for my employer - automatic disclaimer
follows>
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