mplayer needs to use the modern high resolution posix timers interface
rather than the kludgly old rtc or busy waiting methods for timing.
** Package changed: linux (Ubuntu) => mplayer (Ubuntu)
** Changed in: mplayer (Ubuntu)
Importance: Undecided => Medium
** Changed in: mplayer (Ubuntu)
Status: Confirmed => Triaged
** Summary changed:
- rtc: max-user-freq too low for multimedia apps
+ use modern hrtimers
** Changed in: mplayer (Ubuntu)
Assignee: (unassigned) => Phillip Susi (psusi)
** Description changed:
- Binary package hint: linux-source-2.6.22
-
- Hi,
-
- some apps can use the RTC in order to optimize video playback to avoid
- tearing, etc. For MythTV and MPlayer, /dev/rtc/max-user-freq should be
- set to 1024 to enable this functionality. However, it's set to 64 by
- default. MYthTV will fall back on a worse video timing method.
-
- Here's an excerpt from the MythTV wiki on this matter:
-
- "If MythTV will be using the RTC to time the display, it will usually
- request a high interrupt frequency, allowing it to time frames more
- precisely. However, unless MythFrontend is a privileged process, the
- highest frequency that it can request by default is 64 Hz. This is
- usually not sufficient for CRT monitors that are often set to a higher
- frequency, usually 85 or 100 Hz, as well as some LCD screens and
- projectors that can accept various frequencies, producing the tearing
- artifacts as mentioned earlier. The most common solution is simply to
- increase the maximum frequency that an unprivileged process can request
- from the RTC."
-
- IMHO, /dev/rtc/max-user-freq should be set to 1024 by default. I tried
- to set dev/hpet/max-user-freq because HPET seems to be the way to go
- nowadays, but that didn't work. I still had to set /dev/rtc/max-user-
- freq to 1024 to make MythTV work with RTC video timing.
+ Mplayer prefers to use the old /dev/rtc device to generate high
+ resolution interrupts for it to wait on for timing purposes. This
+ interface can only be used by a single task on the system and is
+ wasteful of cpu and power. When this is not available, or not
+ configured to allow setting 1024 interrupts per second ( it isn't by
+ default ), it falls back to wasteful busy waiting. It needs patched to
+ use modern posix timers that can use the modern tickless and HPET kernel
+ features to allow the cpu to remain in deep low power state until the
+ exact time requested.
** Changed in: mplayer (Ubuntu)
Importance: Medium => Wishlist
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https://bugs.launchpad.net/bugs/139949
Title:
use modern hrtimers
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