Theo Verelst Local Diary Page 85

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Oct 14, 00:46, 2009

More power TV

An improvement to get pretty good "surround" TV sound like the last page showed is to use the beamer on the media machine with good and short cable connection (ground breaker and split amp) , lots of VDPau filtering of the uncompressed signal, create the surround (rear) channel using the setup with filter and inverter from the last page at 96kHz sampling rate from the builtin DA converter (Intel precision or so, not great but not very bad either) and I now used the second receivers´audio piped through another DA converter at the reveiver rate of 32kS/s which is of good quality, like so:

I used  my hacked vdpau mplayer for 16:9 limiting and the beamer can magnifi the 10 % extra to make the whole 2 meter 30 wide screen full, and the main audio system is the main studio sytem, with lots of watts and very full range.

For remote viewing (over ethernet) I tried to start up and use the media machine "headless", meaning no screen connected to it, which is possible, I had to at least make the video and sound devices available by hand though, because otherwise that happens at login, which now doesn+t happen. To load all kernel modules and get all running, this was enough I think:

modprobe saa7134-alsa
modinfo video4linux2
modprobe videodev
modprobe videobuf_dma_sg
modprobe videobuf_core
modprobe saa7134
chmod 666 /dev/video*
chmod 666 /dev/dsp*

I don´t know about the kernel modules except the first (which isn´t autoloaded) but the last two commands were needed. To set the channel for one of the two video tuners, mplayer can be used with no output:

~theo/Mplayer/mplayer-export-2009-05-27/mplayer  -af volume=-0:resample=4 8000:0:2 -vo null -tv driver=v4l2:input=0:width=768:height=576:audiorate=32000:adevice=/dev/dsp2:device=/dev/video1:immediatemode=0:volume=100:amode=1:norm=PAL:outfmt=bgr24:freq=248.250    tv://

the freq parameter gets remembered after immedeately quitting it again, and using the same scripts as shown on the previous page. The audio device names/numbers may change after restart, so must be checked. When being away from the machine (with a long ethernet cable in between), it can be fully stopped at the end of the video session by the remotely issued command:

shutdown -P now

All cool.

Reviving the sat computer

Not sounding very reliable, I mucked up the windows partition of a years old supermaket machine (literally, but it was over a 1000 euro at the time), a still noticable Pentium D 3GHz beast with nice shiny fron and lots of connections. I did that when installing a new graphics card into it after the old ones´ fan had worn out (and it´s astrays were full of bubblegum) and I wanted a (cheap, 80 euros) CUDA capable card instead, with additional VDpau and half a Gig of memory. Somehow I forgot to set disc caching on the main sata disk to off when I restarted windows XP on the original partition (with sat receiver software on it) by switching power off... Normally I never do such a thing, and so it was fine for years, doing a lot of BBC sat viewing, but unfortunately ntfs is not so cool as the Linux ext3 file systems with journalling, so the windows partition was messed up, and of course try-it-anyhow restart didn´t make it all better, so as a consequence windows only starts in safe mode. I´m sure I could fix it, but haven´t felt like it. The data is of course available from the also present and fine working (thus far) Linux Fedora 10/64bit partitions.

But I had not more sat: the very cheap satbox coming with the camping-size antenna had died already years ago, and now the sat windows was unfunctional..

Until some days ago I had the nerve to try out if I could load and initialize the proper kernel modulas and software to get the dual tuner terrestial and satellite part of the digitizer card to work on Linux (I´d never bothered to try). Well first I had no luck, but after some compiling of dvbutils (I had all kinds of wrong versions) a kernel update a w_scan install or so and additional (but in Fedora already present) kernel module invocations and some internet reading about utils and frequencies, SPIDs and channel list locations (they´re also on Fedora coming with sat software) for various sats, and a redirecting of the sat antenna as I recall it used to be aimed (its on a wooden pole and the plastic antenna even blows off with very hard wind...) I did get some signal with command line programs to set frequency and to check for signal presence!

I found that dvb (sat) utils were in my (very recent (self) compile) mplayer, and so did the effort of finding out two scan programs and channel list formats, scanned the channels on a sat I thought I received, and: I got some channels to work! Well, well.

A long scan after redirecting the antenna and rethinking which sat it would be aimed most to (the 28 degrees ones) more than a few channels would at least work somewhat or quite, and I found I could even use the two inputs of the sat card for receiving different channels, but the second one with a bit of noise.

And then the more fun thing: I found out I can receive HD with it as well: ITV HD (which isn´t broadcastin more than a text though, and more interestingly: BBC HD, which has a percent or so bit errors (if I can believe the test tool) which is a but much, but it does get received at the full 22megabit  per second for the whole channel, of which then some streams are for the HD, and it plays, too, even live albeit that the errors make mplayer get out of sync, so its doesn´t sync good and becomes noise after a little while. Interesting, but far from perfect.