Video Encoding

Using ffmpeg

On Kubuntu 8.10 (Intrepid) this meant getting ffmpeg by doing something along the lines of:

sudo apt-get install ffmpeg libavcodec-unstripped-51 libavdevice-unstripped-52 \
    libavformat-unstripped-52 libavutil49 libpostproc-unstripped-51 libswscale0

Then to convert a quicktime video from my camera i would run:

ffmpeg -f mov -i p1010258.mov -vcodec libxvid -s 240x160 -qscale 10 -ab 48k -ar 22050 -ac 1 -acodec libmp3lame test.avi

This basically means in short:

• take the quicktime movie (-f mov)
• by the name (-i p1010258.mov)
• convert it to ISO MPEG4 (-vcodec libxvid)
• optionally scale it (-s 240x160)
• requantize it to reduce its size (-qscale 10)
• set the audio bitrate (-ab 48k)
• with a sample rate (-ar 22050)
• and one channel, mono (-ac 1)
• using the lame encoder (-acodec libmp3lame)
• and finally call the output (test.avi)

I think the -f mov -i p1010258.mov order makes a difference, because it failed for me the other way around.

One way to find out what format a video is, is to run tcprobe, which comes with transcode, discussed below. In our example that would be something like:

# tcprobe -i p1010258.mov
[tcprobe] Apple QuickTime movie file
[probe_mov.c] audio codec=raw
[probe_mov.c] video codec=jpeg
[tcprobe] summary for otrs/p1010258.mov, (*) = not default, 0 = not detected
import frame size: -g 640x480 [720x576] (*)
       frame rate: -f 30.000 [25.000] frc=5 (*)
      audio track: -a 0 [0] -e 8000,8,1 [48000,16,2] -n 0x1 [0x2000] (*)
           length: 555 frames, frame_time=33 msec, duration=0:00:18.500

tcprobe doesn't always work, in which case opening the file in a media player and looking at the clip properties might help.

Using DVD::Rip

Of course armed with this new knowledge i decided to find out what it takes for DVDs. It helped to get the most excellent DVD::Rip and of course transcode. Again, on Kubuntu i ran:

sudo apt-get install dvdrip

After running DVD::Rip for the first time it greets you with a wizard to specify defaults and check dependencies. The dependency check is incredibly helpful, and i recommend getting whatever is missing. Usually adept or synaptic are pretty helpful with this. With this out of the way, here's a sample project.

1. After opening DVD::Rip create a new project.

2. Then rip your desired track off the DVD (In my case an easy choice, but usually the largest track).

3. Adjust your image as desired.

• After picking a preview frame, i first selected "No modifications" and hit "Apply Preset Values"
• Then i entered 240 in the Zoom - Width Field followed by hitting "Calc Height"

4. Adjust transcode as needed. Relevant items are:

• Container AVI
• Video Codec xvid
• 2 Pass encoding No
• Audio MP3
• Bitrate 48kbits
• I initially set the frame range for testing on a small sample.
• The transcode options -E 22050,0,1. I set -E for the third '1'(Mono) parameter, otherwise i could have used the hz field next to the bitrate above.
• Finally -o /tmp/test.mp4 or wherever the output is to be stored.

5. Now for some reason, when doing only partial frames, DVD::Rip does something after it converts the fragment that takes a lot of time and is really hard to kill. So for testing i run transcode from the command line. To get the command you can either goto "Debug - Show Transcode commands" or just hit CTRL-t. Then scroll down to "Transcode Command:"

6. Then run a slightly trimmed down version of that from the command line.

transcode -J normalize -Y 2,0,2,0 -L 19390 -w 2540,50 -i /tmp/dvdrip-data/sample/vob/001/ \
 -y xvid -M 2 -Z 240x180 --print_status 25 --a52_drc_off -E 22050,0,1 -x vob -b 48,0,2 -a 0 \
 -H 10 -o /tmp/test.mp4 -c 10-510 -f 24,1

7. Test the video and repeat until the result is desirable. Then take out the frame range parameters and just hit the "Transcode" button.