Trickplay

The renderer makes the decision about when frames
are dropped. If the user specified that it
should autoswitch from all-frames mode to keyframe-mode,
then the renderer will try to play all the frames
it can. When it realizes that it is dropping frames
about a certain rate, then it will tell the client
core that it wants to go to keyframe-mode. At that
point, the client core tells the file format plugin
that it is going to keyframe mode.

The file format may or may not at that point start
providing just keyframes. But the fileformat proxy
in the client core will from that point on filter
out everything but keyframe packets.

Does that answer your question?

Eric

=============================================
Eric Hyche (ehychereal.com)
Technical Lead
RealNetworks, Inc.  

> -----Original Message-----
> From: gang.1.shennokia.com [mailto:gang.1.shennokia.com] 
> Sent: Thursday, June 07, 2007 12:42 PM
> To: ehychereal.com; helix-client-devhelixcommunity.org
> Subject: Trickplay 
> 
> Hi, Eric, 
> 
> I have a question regarding "trickplay"
design in 
> https://helix-client.helixcommunity.org/nonav/2005
/devdocs/TKP
> -SOD-001-TrickPlay.html 
> <https://helix-client.helixcommunity.org/nonav/2005/
devdocs/TK
> P-SOD-001-TrickPlay.html> .
> 
> How does Helix avoid a overflow during fast forward? If

> fileformat (optionally) deliver packets differently
based on 
> the magnitude of the playback velocity, there would be
more 
> packets delivered to video renderer than needed in a
fast 
> forward playback. Which component will drop these extra
frames?
> 
> Thanks, 
> 
> Gang Shen 
> 
> 


_______________________________________________
Helix-client-dev mailing list
Helix-client-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinf
o/helix-client-dev

Thanks a lot. That answers my question. 

It looks like there is a need for renderer to selectively
push frames
(non-key frames) to decoders based on magnitude of velocity,
for
all-frames mode. That would save decoder from decoding
frames that are
supposed to be skipped. Is that what Helix has in its video
renderer?
Btw, my concern is on our MDF renderer; we'd like to see how
Helix
renderer works. 

-GS

-----Original Message-----
From: ext Eric Hyche [mailto:ehychereal.com] 
Sent: Thursday, June 07, 2007 12:00 PM
To: Shen Gang.1 (Nokia-TP-MSW/Dallas);
helix-client-devhelixcommunity.org
Subject: RE: Trickplay 


The renderer makes the decision about when frames are
dropped. If the
user specified that it should autoswitch from all-frames
mode to
keyframe-mode, then the renderer will try to play all the
frames it can.
When it realizes that it is dropping frames about a certain
rate, then
it will tell the client core that it wants to go to
keyframe-mode. At
that point, the client core tells the file format plugin
that it is
going to keyframe mode.

The file format may or may not at that point start providing
just
keyframes. But the fileformat proxy in the client core will
from that
point on filter out everything but keyframe packets.

Does that answer your question?

Eric

=============================================
Eric Hyche (ehychereal.com)
Technical Lead
RealNetworks, Inc.  

> -----Original Message-----
> From: gang.1.shennokia.com [mailto:gang.1.shennokia.com]
> Sent: Thursday, June 07, 2007 12:42 PM
> To: ehychereal.com; helix-client-devhelixcommunity.org
> Subject: Trickplay
> 
> Hi, Eric,
> 
> I have a question regarding "trickplay"
design in 
> https://helix-client.helixcommunity.org/nonav/2005
/devdocs/TKP
> -SOD-001-TrickPlay.html
> <https://helix-client.helixcommunity.org/nonav/2005/
devdocs/TK
> P-SOD-001-TrickPlay.html> .
> 
> How does Helix avoid a overflow during fast forward? If
fileformat 
> (optionally) deliver packets differently based on the
magnitude of the

> playback velocity, there would be more packets
delivered to video 
> renderer than needed in a fast forward playback. Which
component will 
> drop these extra frames?
> 
> Thanks,
> 
> Gang Shen
> 
> 


_______________________________________________
Helix-client-dev mailing list
Helix-client-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinf
o/helix-client-dev

> -----Original Message-----
> From: gang.1.shennokia.com [mailto:gang.1.shennokia.com] 
> Sent: Thursday, June 07, 2007 2:36 PM
> To: ehychereal.com; helix-client-devhelixcommunity.org
> Subject: RE: Trickplay 
> 
> 
> Thanks a lot. That answers my question. 
> 
> It looks like there is a need for renderer to
selectively push frames
> (non-key frames) to decoders based on magnitude of
velocity, for
> all-frames mode. That would save decoder from decoding
frames that are
> supposed to be skipped. Is that what Helix has in its
video renderer?
> Btw, my concern is on our MDF renderer; we'd like to
see how Helix
> renderer works. 
> 

In the base video renderer (from which the RealVideo
renderer and
MP4 video renderer and WMV renderer derive), we have decided
to
try and render as much as we can in all-frames mode before
switching
to keyframe mode. Of course, the TLC can override this
decision
by simply setting keyframe mode to TRUE when it calls
SetVelocity().
If you *know* on your platform, for instance, that
all-frames mode
is not feasible beyond 1x or 2x then you can always have the
TLC
enforce that when it calls SetVelocity.

Eric

> -GS
> 
> -----Original Message-----
> From: ext Eric Hyche [mailto:ehychereal.com]

> Sent: Thursday, June 07, 2007 12:00 PM
> To: Shen Gang.1 (Nokia-TP-MSW/Dallas);
> helix-client-devhelixcommunity.org
> Subject: RE: Trickplay 
> 
> 
> The renderer makes the decision about when frames are
dropped. If the
> user specified that it should autoswitch from
all-frames mode to
> keyframe-mode, then the renderer will try to play all
the 
> frames it can.
> When it realizes that it is dropping frames about a
certain rate, then
> it will tell the client core that it wants to go to
keyframe-mode. At
> that point, the client core tells the file format
plugin that it is
> going to keyframe mode.
> 
> The file format may or may not at that point start
providing just
> keyframes. But the fileformat proxy in the client core
will from that
> point on filter out everything but keyframe packets.
> 
> Does that answer your question?
> 
> Eric
> 
> =============================================
> Eric Hyche (ehychereal.com)
> Technical Lead
> RealNetworks, Inc.  
> 
> > -----Original Message-----
> > From: gang.1.shennokia.com
[mailto:gang.1.shennokia.com]
> > Sent: Thursday, June 07, 2007 12:42 PM
> > To: ehychereal.com; helix-client-devhelixcommunity.org
> > Subject: Trickplay
> > 
> > Hi, Eric,
> > 
> > I have a question regarding "trickplay"
design in 
> > https://helix-client.helixcommunity.org/nonav/2005
/devdocs/TKP
> > -SOD-001-TrickPlay.html
> > <https://helix-client.helixcommunity.org/nonav/2005/
devdocs/TK
> > P-SOD-001-TrickPlay.html> .
> > 
> > How does Helix avoid a overflow during fast
forward? If fileformat 
> > (optionally) deliver packets differently based on
the 
> magnitude of the
> 
> > playback velocity, there would be more packets
delivered to video 
> > renderer than needed in a fast forward playback.
Which 
> component will 
> > drop these extra frames?
> > 
> > Thanks,
> > 
> > Gang Shen
> > 
> > 
> 


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Helix-client-devhelixcommunity.org
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