This is the video I tried the process on: download

To try this out yourself, you will first need to have mplayer installed. If you are running Debian/Ubuntu, do this,

sudo apt-get install mplayer

After this, download the video using the link provided above. Run this command,

mplayer -lavdopts vismv=1 -vo x11 motion_vector_video.avi

To learn more about motion compensation, go here.
Enjoy!

There is a simple way to generate thumbnails in Linux using ffmpeg, a very very useful tool for processing videos. Let us generate a thumbnail for this video. Download the video and rename it to test.avi.

Then, run this command,

ffmpeg  -itsoffset -4  -i test.avi -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 test.jpg

This command generates a 320×240 sized PNG thumbnail at the 4th second in the video. The output looks like this.

If you do not have ffmpeg installed and are using Debian/Ubuntu, do,

sudo apt-get install ffmpeg

A series of thumbnails, at 4, 8, 12 and 16 seconds.

ffmpeg  -itsoffset -4  -i test.avi -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 test.jpg
ffmpeg  -itsoffset -8  -i test.avi -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 test.jpg
ffmpeg  -itsoffset -12  -i test.avi -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 test.jpg
ffmpeg  -itsoffset -16  -i test.avi -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 test.jpg

useful links

• Create a random thumbnail of a video file
• http://www.danielfischer.com/2007/06/27/how-to-use-ffmpeg-to-convert-video-via-ruby-on-rails/

Happy thumbnailing!

The card is available through Amazon.com.
Pinnacle PCTV Analog PCI 50i – TV / radio tuner / video input adapter – PCI – SECAM, PAL

Setting up the card in Linux

I have Ubuntu Gutsy installed (7.10) and followed this guide to setup the card and the instructions worked like a charm. A gist of the procedure.

Ubuntu Gutsy recognizes the card automatically, the following commands help to check if the recognition happened or not. Both commands should give atleast one line of output each.

sudo update-pciids
lspci | grep -i saa713
dmesg | grep saa713

Watching TV – tvtime

tvtime is a simple to use application for watching TV on Linux. Here is how you configure it.

sudo apt-get install tvtime
tvtime &

Right click to open a setup menu. You can also hit [F1] or [tab] key to show configuration menu:
Linux Tvtime configuration hit [F1] or [tab] key to show configuration menu
(Fig. 01: Linux tvtime application configuration menu)
First, you need to setup video source, frequencies and channels etc.

Setup video source

Visit Input Configuration > Change Video Source > Setup source as per your setup.

Setup frequencies table

You need to setup the channels you are receiving with the tuner. Here we use europe frequencies table. Visit Channel management > Change Frequency table > Select new table
Scan Channel

Finally, you need to scan for channels by visiting Channel management > Change Frequency table > Scan channels for signal > Back > Exit

Sound configuration

You need to attach internal cables to get sound out of TV tuner card. Use driver saa7134-oss or saa7134-alsa to get sound out of card. This driver get loaded automatically. Open terminal and type the following command to hear the audio through ALSA using tvtime (or other programs that don’t support it directly):

$ sox -c 2 -s -w -r 32000 -t ossdsp /dev/dsp1 -t ossdsp -w -r 32000 /dev/dsp

Recording TV using mencoder

if you do not already have mencoder, you can install it (on Debian/Ubuntu) by doing

Note that the above command will also install mplayer which is useful for viewing video files and tv channels. If you are the command line kind of person, you can do away with tvtime and use mplayer!
To record a TV channel, you will first need to figure out the frequency of the channel. For this I found scantv useful. This command will scan channels in the specified range and print out the found channels. After figuring out the frequency of the channel to record, use this mencoder command to record the video in a compressed format.
mencoder tv:// -tv driver=v4l2:input=0:norm=pal:width=640:height=480:device=/dev/video0:\
freq=775.25:adevice=/dev/dsp1:forceaudio:audiorate=32000 buffersize=64\
 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=400:keyint=30 -oac mp3lame\
-lameopts br=32:cbr:mode=3 -ffourcc divx -o "test.avi"



To use mplayer to view TV directly (without using tvtime),do this.
mplayer tv:// -tv driver=v4l2:input=0:norm=pal:width=640:height=480:device=/dev/video0:\
freq=775.25:adevice=/dev/dsp1:forceaudio:audiorate=32000



I've been using this card without a glitch and recommend for HTPC attempts on Linux.
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