[mythtv] sound during fast forward/rewind on pvr350 when using it for tv-out

Joseph A. Caputo jcaputo1 at comcast.net
Sat Mar 20 23:44:29 EST 2004

jose rubio wrote:
> On Fri, 2004-03-19 at 16:07, Joseph A. Caputo wrote:
>>On Friday 19 March 2004 15:38, jose rubio wrote:
>>>On Thu, 2004-03-18 at 12:45, Joseph A. Caputo wrote:
>>>>On Thursday 18 March 2004 11:57, Simon Kenyon wrote:
>>>>>David Engel wrote:
>>>>>>On Thu, Mar 18, 2004 at 01:49:44PM +0000, Simon Kenyon wrote:
>>>>>>>with ivtv-fb. when i fast forward to rewind then it plays brief
>>>>>>>sequences of video as it goes. unfortunately, it also plays
>>>>>>>brief snatches of audio as well, which IMHO is annoying. this
>>>>>>>does not
>>>>>>It's a known problem.  I don't know when it will get fixed since
>>>>>>it requires a significant change to the way Myth does ff/rew.
>>>>>oh well. i'll have to live with it so
>>>>>thanks for the quick answer
>>>>You could use the 'trick play' feature instead of bona-fide ff/rew.
>>>>+ gives 'smooth' rather than 'jumpy' ff/rew
>>>>- requires more CPU, as it actually decodes every frame, as opposed
>>>>to skipping them like ff/rew does
>>>>- max. speed is lower than ff/rew
>>>>That said, I think ff/rew should be able to be re-worked so that it
>>>>doesn't play sound.  Trick play obviously does it.
>>>>This has been an item on my list for a long time.  I wrote the
>>>>initial implementation of the current ff/rew behavior, and at the
>>>>time there was no clean way to mute the sound during ff/rew without
>>>>modifying NuppelVideoPlayer, which Isaac didn't want me to do at
>>>>the time.  Later the 'mute' functionality was added, and I thought
>>>>I might be able to utilize that, but it would have been a kludge,
>>>>and since the mute function doesn't maintain state, there was no
>>>>elegant way to determine if the sound should remain muted or not
>>>>when exiting ff/rew.  Then the trick play features were added, and
>>>>I seem to recall ended up touching NuppelVideoPlayer to do
>>>>things... I guess the author was able to make a better argument
>>>>than I did at the time.
>>>>Maybe I'll revisit this, but actually it's not a priority right
>>>>now; I think I'm going to remap my ff/rew keys to do trick play. 
>>>>Anyone else is welcome to take a stab at it...
>>>OK so I'm gonna sound stupid here but...
>>>What is the 'trick play' feature?
>>Speed up/slow down playback.  According to keys.txt:
>>- U to increase the play speed
>>- J to decrease the play speed
>>This is different than ff/rew, as I've described... the 'trick play' 
>>features give a smoother playback, since they're not skipping frames 
>>but simply changing the playback rate.  For fast playback this of 
>>course this means decoding more frames per second, so it comes at the 
>>expense of a higher CPU load (if I had to guess, anyway).
> Oh yes, I've tried that.  Only problem is that the fastest it goes is
> 3X...  Took a quick look at the code and it seems to allow up to 5X. 
> Don't know much about the code though :-( so I'm not sure if I could
> make it go faster.  Do you know?
> -jose-

My guess is the speed limit in the code is merely a throttle to prevent 
you from trying to increase playback speed beyond what your CPU can 
realistically handle.  But that's just a guess.


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