Does this explain TV-Out configuration? [LWN.net]

Does this explain TV-Out configuration?

Posted Jan 23, 2007 13:44 UTC (Tue) by rankincj (guest, #4865)
In reply to: CRTCs vs. outputs by daenzer
Parent article: LCA: Updates on the X Window System

Is this why the TV-Out instructions on my old G400 MAX and Radeon 9200 video cards say that the monitor will be driven at the same frequency as the TV, and so anyone intending to use a PAL TV should be sure that the monitor is happy running at 50 Hz? This is one restriction I would really like to avoid!

Does this explain TV-Out configuration?

Posted Jan 23, 2007 15:58 UTC (Tue) by jzbiciak (guest, #5246) [Link]

Does the TV Out display the same thing as the monitor? If so, then there's probably only one display generation pipeline that feeds to multiple physical outputs. My interpretation of the CRTC abstraction is that it also allows a single display controller to control multiple heads, each potentially displaying something different.

Even then it seems like you might get into restrictions on refresh rates or pixel clocks between the two outputs if there is only one pixel clock source, or if there are synchronization requirements between the two pipelines during refresh. I haven't looked closely at modern display hardware, though, so I really couldn't say.