Asf fastforward performance
- From: Wael_Bakr <WaelBakr@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Thu, 26 May 2005 01:51:01 -0700
Hi All
I develop an application that reads an Asf Mpeg4 file that contains
1 audio and 3 video streams , i want the application to perform
a playback of fastforward of 3 times the normal playback speed
without chopping (I.e i wants the fastforward to be completely
smooth without any chopiness)
i do this by implementing the GetPrivateTime() function of
CBaseReferenceClock class as follows:
REFERENCE_TIME CMyRefClock::GetPrivateTime()
{
CAutoLock cObjectLock(this);
/* If the clock has wrapped then the current time will be less than
* the last time we were notified so add on the extra milliseconds
*
* The time period is long enough so that the likelihood of
* successive calls spanning the clock cycle is not considered.
*/
DWORD dwTime = timeGetTime();
{
m_rtPrivateTime += Int32x32To64(UNITS / MILLISECONDS,
(DWORD)(m_clock_speed*(dwTime - m_dwPrevSystemTime)));
m_dwPrevSystemTime = dwTime;
}
return m_rtPrivateTime;
}
so as you can see the idea is to multiply the elapsed time by the
m_clock_speed variable (which has the value of 3 in my case)
by doing that , i make the reference time passes with 3 time the
normal speed , so the playback speed also becomes multiplied by
3 , which gives me 3 times the normal playback speed.
while this gives me a very smooth playback without chpiness , the
maximum performance i can get is 2 times the normal playback
speed no matter what , i heared that the ATI Radeon X800 has
a built in mpeg4 acceleration so i tried it but it can't exceed the
2 times the normal playback speed ,
does anyone have any idea how can i enhance the performance to
get the full 3 time normal playback speed , or where it could be the
performance bottleneck ?
Thanks,
.
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