[Softdevice-devel] Slow motion, fast forward/rewind and sound

Marko Mäkelä marko.makela at hut.fi
Sat May 14 21:59:51 CEST 2005


I remember getting a crash some weeks ago when playing with the slow motion,
pause and fast forward/rewind keys in rapid succession.  I might have got
that kind of a crash last week when I was viewing something in slow motion.
It was a 4:3 program, no subtitles, most likely with mono sound (unless
DVB-T is always stereo).  Could there be some buffer overflow?

If I remember correctly, the audio will take a while to catch up after
restoring normal playback speed.  I guess this could also be because the
audio packets are being sent a few frames earlier than the corresponding
video frames.

A crazy idea: Would it be possible to play the audio also in fast-forward
mode?  If possible, offer two options: (a) decode and play every nth audio
frame, producing a chopping sound, or (b) decode everything and play every
nth sample, producing a high-pitched sound.  This would be useful when
watching slow-paced programs that lack subtitles.

This is definitely not a top priority thing, but it would most probably
differentiate softdevice from all full-featured cards and proprietary
recorders.  If you feel like it, implement these also for slow motion
and rewind, but not for the 1-minute skip. :-) Pitch correction could be
optional.

The credit for this idea goes to a friend of mine who was struggling with
math exams about 10 years ago.  The lectures were broadcast on campus TV,
and he had recorded them on his VCR.  When I visited him in the evening
before the exam, he was wondering whether he should modify his VCR to not
mute the sound during fast forward.  There was not enough time before the
exam to watch all the lectures at normal speed.

	Marko



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