Advanced Display
From Plex
Tuning The Display for Proper Resolution and Refresh Rates
When connecting an External Display ( Plasma/LCD/Projector/HDTV ) to a Mac via DVI or DVI-HDMI, the Mac's internal video card communicates with the display to find an appropriate resolution and refresh rate. This two way interaction is facilitated through EDID, or Extended Display IDentification. Computer monitors typically have a robust implementation of EDID and can properly communicate to the display the native resolution and all supported refresh rates. HDTV's however, can vary in terms of usefulness of supplied EDID information. Although the correct information is buried within the output, it is possible that the initial resolution and refresh rate chosen either is not the native resolution to the respective panel, or is not optimal for 720/1080p viewing.
Furthermore, many HDTV's will default into a PC-type mode, often bypassing built in functionality such as 3:2 pulldown or visual tweaks such as contrast and black level enhancement. In addition, a significant amount LCD and Plasma displays accept and process 1080p or 24hz signals with a native resolution less than or even greater than true 1080p. To make matters even worse, many displays will exhibit over- and under-scanning with standard 720p or 1080p signals. Although Plex has built in support for compensating for Over/Underscan, it is advantageous to properly configure your display before running Plex, as will improve the overall experience with OSX and Plex.
The following guide will assist in finding optimal signal paths from the video output device of the Mac to the Display Device. To properly configure your display, you will need to download a utility called SwitchResX.
http://www.madrau.com/html/SRX/DL.shtml
- While adjusting display parameters, it is possible that to create a signal that is incompatible with the display, thus outputting a blank screen on the displauy. To resolve this issue, there are a few routes to take. Either un-plug and re-plug in the DVI cable, change the display settings using remote desktop, or reboot the system. Adjust the display timings is mostly a process of trial and error.
- Download and Install SwitchResX. It will be located in the Other Pane in System Preferences. Under the Display Tab, click on the "Export EDID" button. This will save a text file to your desktop. Open this file and have it handy, as you will need to reference it many times during this guide.
- Under the section titled "Monitor Description Blocks:" will be a list of the proper timings. For Example, this is a listing for the proper timings of a 1080 60hz signal for a Pioneer Kuro 8G Plasma Display. This information will be used as the reference for this guide.
Detailed Timing Block #1 - Timing definition:
Mode = 1920 x 540 @ 60.053Hz
Pixel Clock............. 74.25 MHz Interlaced
Horizontal Vertical
Active.................. 1920 pixels 540 lines
Front Porch............. 88 pixels 2 lines
Sync Width.............. 44 pixels 5 lines
Back Porch.............. 148 pixels 15 lines
Blanking................ 280 pixels 22 lines
Total................... 2200 pixels 562 lines
Scan Rate............... 33.750 kHz 60.053 Hz
Image Size.............. 1102 mm 620 mm
Border.................. 0 pixels 0 lines
Sync: Digital separate with
* Positive vertical polarity
* Positive horizontal polarity
For this particular display, an 8G Pioneer Kuro Plasma, EDID is proving a 1920x1080 interlaced resolution. It is important to take note of this criteria. Some displays, even with native 1080p support, will provide an interlaced 1080 setting from EDID. When initially connecting this display to a Mac Mini via the default OSX 1920x1080 output, the entire top menu bar was cut off, as well as pixels on the right side of the screen. Using this example, step by step instruction will be provided on how to properly compensate for these issues.
- Under the custom tab in SwitchResX, click the + button to add a custom display setting. A configuration screen will display, with the capability to input settings.
- The settings are not mutually exclusive, and have an effect on each other. It is likely that you will not be able to input the exact parameters that were provided by the EDID output. It is important to follow these guidelines to ensure valid display configurations, to avoid outputting an incorrect signal.
- The Total pixels for Horizontal and Vertical must be the sum of the Active Pixels + the Display Blanking. Since I am using an interlaced signal, I will double the Vertical Active and Blanking pixels to achieve a proper progressive 1080p signal. In this case: [ 540*2 = 1080 ] + [22*2 = 44 ] = 1080+44 = 1124
Equation: Horizontal Total = Active ( Horizontal ) + Horizontal Blanking
Pioneer : 2200 = 1920 + 280
Equation: Vertical Total = Active ( Vertical ) + Vertical Blanking
Pioneer : 1124 = 1080 + 44
- Once the information from the EDID is entered into the custom SwitchResX setting, it is likely that the the image will overscan or underscan in one of both of the Vertical and Horizontal timings. The process of tweaking the aforementioned custom setting will alleviate these issues and provide a stable, correct image. This is where the trial and error begins. To correctly compensate for these issues, refer to the following Diagram.
|------------------Active Horizontal----------------|
-------------------------------------------------------
| /\ | --
| | | |
| Vertical Back Porch | |
| | |
| <------------ Horizontal ----------> | | Active Vertical
| Back Porch Front | |
| | |
| Vertical Front Porch | |
| | | |
| \/ | --
--------------------------------------------------------
| Display |
------------------------------
- If the image is too large for the display, then reduce the amount of pixels in the 'active' parameter. Remembering the equation for the Total H/V pixels, you must compensate the Front/Back Porch Values. Note, the 'Sync Width' values should never change.
Example: The Image is overscanning in the horizontal direction. Reduce the 'Active' by 20 Pixels ( 1920-20=1900). Now add 20/2 = 10 pixels to both the Horizontal Front and Back Porch. The results will be 1900+98+158+44= 2200. If the total is off ( in this case !=2200 ), then the display settings with be invalid, and non-usable by the display device.
- If the image is shifted off screen in either the X or Y axis, in any direction, then the Porch Values need to be adjusted. To move the image to the left, increase the Horizontal Front Porch, and Decrease the Horizontal Front Porch. To move the image upwards, increase the Vertical Front Porch, and decrease the Back Porch. Inverse these adjustments respective for left/right, up/down adjustment. Just remember that whatever is taken out of front or back porch must be filled into the opposite porch. Again, mind the original Total Equation, so that all values add up to the Horizontal and Vertical Totals.
Example: The image is shifted to the top, cutting off the OSX Menu bar. In this case, try reducing the Vertical Front Porch and increasing the Back Porch. Keep in mind that the EDID data used in this example was interlaced, so Vertical values must be doubled. To slide the image downward, reduce the Front Porch by 4 pixels, and increasing the Back Porch by 4. Our Remaining equation is : 1080 (Active ) + 0 ( Front Porch ) + 34 ( back porch ) + 10 ( Sync Width ) = 1124 (vertical total).
Using refresh rates other than 60 hz
Refer to the previous section for information about how to extract EDID information from the display. This section is in reference to Plex 7.1, as Plex 5-Series has audio sync issues with non-standard refresh rates.
Film is naturally 24 frames per second. The issue of displaying 24 frames evenly in a 60 hz cannot be solved without incorporating a sequence of frame repeating, such as the 3:2 sequenced used in DVDs. Fortunately many displays now support refresh rates that are multiples of the frame rate used for Film. They range from 48hz ( 2:2 frame sequence ), 72hz ( 3:3), up to 120hz ( 4:4 ). With powerful hardware alongside Plex, it is possible now to display 24 hz ( 23.976 fps ) encoded video, if a proper display configuration is used. The standard output used for Blu-Ray playback is 1080p/24hz. If you have proper EDID information for a 24/48/72/120hz setting for your display, it is possible to pass a true 24fps signal from Plex.
Following the guidelines from the previous sequence, with some trial and error thrown in, I was able to to find a 1080p/24 signal to be used with a Kuro 8G Display. Unfortunately, this brings up new issues with 25 and 30 fps material, with the need to revert back to a 60hz refresh rate for proper playback.
In the future, a small database can be created as a reference to all users. Use this section to upload settings for specific configurations. I.e. Pioneer Kuro 8G / Mini, Sony Bravia 42" XBR5 / MacBook Pro.