From MythTV Official Wiki
Check error messages
Start mythfrontend from a terminal window, so that you can see if there are any error messages.
If you get an error message like
then see: Troubleshooting:Prebuffering_pause
- Default Settings.
- Start off by not overclocking, don't run in turbo mode. Performance is nothing without stability. Once your system is working, you can return to the overclocked setting.
- AGP Fast Writes.
- Enable / disable. For some motherboards, enabling this option causes instability, it should help improve performance when enabled.
- PCI Latency.
- Set to lowest setting and gradually increase it if there are extra issues.
- Assuming a proprietary graphics card is being used, make use of the official drivers from the manufacturer. And make sure your cards GPU is listed as being supported with the driver version.
- Timer Frequency.
- By setting the kernel to use 1000HZ, it is suitable for both PAL and NTSC playback / recording.
- Disable kernel preemption. Some people report faster systems with preemption enabled, but it might interrupt video playback more than it helps.
- If your disks can use it (and they really should), make sure DMA (Direct Memory Access) is enabled.