On Mon, 16 Apr 2007, Attila Kinali wrote:
The issue of stream synchronus playback can be entirely
solved in software and does not need to be done in hardware.
Unless you need A-V sync below 0.5*frame-time, then you need
at least a little bit information from the graphics card, when
the current image drawing is finished, but any half decend card
supports this.
The problem is _not_ A-V sync, but interference jitter between different
frame rates. Please have alook at:
http://www.linuxtv.org/wiki/index.php/The_DVB_Decoder_Challenge#Screen.2FDecoder_Sync_Aliasing
If you imagine multiplying two square wave signals of different
frequencies (like 50Hz for deinterlaced framerate and 60Hz refresh of the
monitor...) and the resulting signal/spectrum. Then compare that to a case
where both signals are of same frequency and in phase... Drawing some
graphs on a piece of cross-ruled paper will help :) That will show the
need for hw-capability of runtime adjusting of pixel clock around one
permille. The means of adjusting may be quite rudimentary like flipping
clock synthesizer dividers back and forth with adjustable duty cycle.
Synthesizer response time needs to be set low enough so that it does
averaging of the pulses.
-Vesa
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