4.17. Zr
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## 4.17. Zr

This is a display-driver (`-vo zr`) for a number of MJPEG capture/playback cards (tested for DC10+ and Buz, and it should work for the LML33, the DC10). The driver works by encoding the frame to JPEG and then sending it to the card. For the JPEG encoding `libavcodec` is used, and required. With the special cinerama mode, you can watch movies in true wide screen provided that you have two beamers and two MJPEG cards. Depending on resolution and quality settings, this driver may require a lot of CPU power, remember to specify `-framedrop` if your machine is too slow. Note: My AMD K6-2 350MHz is (with `-framedrop`) quite adequate for watching VCD sized material and downscaled movies.

This driver talks to the kernel driver available at http://mjpeg.sf.net, so you must get it working first. The presence of an MJPEG card is autodetected by the `configure` script, if autodetection fails, force detection with

    ./configure --enable-zr

The output can be controlled by several options, a long description of the options can be found in the man page, a short list of options can be viewed by running

    mplayer -zrhelp

Things like scaling and the OSD (on screen display) are not handled by this driver but can be done using the video filters. For example, suppose that you have a movie with a resolution of 512x272 and you want to view it fullscreen on your DC10+. There are three main possibilities, you may scale the movie to a width of 768, 384 or 192. For performance and quality reasons, I would choose to scale the movie to 384x204 using the fast bilinear software scaler. The command line is

    mplayer -vo zr -sws 0 -vf scale=384:204 movie.avi

Cropping can be done by the `crop` filter and by this driver itself. Suppose that a movie is too wide for display on your Buz and that you want to use `-zrcrop` to make the movie less wide, then you would issue the following command

    mplayer -vo zr -zrcrop 720x320+80+0 benhur.avi

if you want to use the `crop` filter, you would do

    mplayer -vo zr -vf crop=720:320:80:0 benhur.avi

Extra occurrences of `-zrcrop` invoke cinerama mode, i.e. you can distribute the movie over several TVs or beamers to create a larger screen. Suppose you have two beamers. The left one is connected to your Buz at `/dev/video1` and the right one is connected to your DC10+ at `/dev/video0`. The movie has a resolution of 704x288. Suppose also that you want the right beamer in black and white and that the left beamer should have JPEG frames at quality 10, then you would issue the following command

    mplayer -vo zr -zrdev /dev/video0 -zrcrop 352x288+352+0 -zrxdoff 0 -zrbw \
        -zrcrop 352x288+0+0 -zrdev /dev/video1 -zrquality 10 \
            movie.avi

You see that the options appearing before the second `-zrcrop` only apply to the DC10+ and that the options after the second `-zrcrop` apply to the Buz. The maximum number of MJPEG cards participating in cinerama is four, so you can build a 2x2 vidiwall.

Finally an important remark: Do not start or stop XawTV on the playback device during playback, it will crash your computer. It is, however, fine to FIRST start XawTV, THEN start MPlayer, wait for MPlayer to finish and THEN stop XawTV.

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