2008.02_Media Magnate-Sound, Video, and News at the Command Line.pdf

Sound, Video, and News at the Command Line

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Learn more about Linux text-based multimedia utilities for playing streams, editing images, and reading CDs

or DVDs from the command-line.

By Kristian Kißling

Janski, photocase.com

Most users associate multimedia tools with the standard GUI desktop and bright graphical effects, but Linux

comes with tools for playing streams, editing images, and reading CDs or DVDs from the command line. In

this article, I describe some Linux text-based multimedia utilities.

Video in Three Steps

The Mencoder console tool lets users convert movies into other formats while scaling a multi-gigabyte DVD

movie to lean MPEG4 material that will fit on a CD. To do so, Mencoder uses the Ffmpeg codecs. To view

the results, you will need to enable the framebuffer. The repository list in Table 1 shows which external

package sources you need to install for Mendoder and other individual programs as an Ubuntu or SUSE user

and what alternatives are available.

The normal approach to converting a DVD comprises three steps (three-pass encoding): start by ripping the

audio track, then transcode the video from VOB format to MPEG4 format, and drop the audio track on top of

it. Depending on the data you have grabbed, the last step enhances the quality of the movie. I'll take this

method one step at a time.To see the titles and chapters on a DVD, use mplayer -identify -nosound -novideo

dvd:// . The command

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$ mencoder -oac mp3lame -lameopt

s br=96:cbr:vol=6 -ovc frameno -

o target.avi dvd://7

then extracts the audio track from title seven, for example, of the DVD in the drive and stores the results in

target.avi . Table 2 explains what the parameters in this command do.

Next comes a step to determine the crop values. To find out which part of the raw material you need to crop to

remove the black stripes at the edges, you need to set the cropdetect option:

$ mencoder -sws 2 -oac copy -ovc

lavc -lavcopts vcodec=mpeg4:vhq

:vbitrate=629:vpass=1 -vf cropde

tect,scale=720:480 -o target.avi dvd://7

After starting the process, the command line outputs the required crop values after about 10 seconds (Figure

1). Replace cropdetect with the displayed crop value, such as crop=720:640:0:0 .

Figure 1: Mencoder compresses DVD movies enough to fit them onto a CD, which requires converting the

original material into another format.

Now it's time to start phase two, which will produce the first rough version of the movie. Table 3 explains the

numerous options.

Now for the last trick: Phase three. Use the same command line, but replace vpass=1 with vpass=2 . What's

the difference? This time, the program uses the logfile created at the previous pass and enhances the quality of

the resulting movie on the basis of information in the file.

A detailed description is beyond the scope of this article, but numerous online guides can help [1][2][3].

Check out the Mencoder man pages for fine-tuning tips ( man mencoder ).

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Screen Shots

The command line also has much to offer in the image manipulation field. For example, the FBGrab tool lets

users grab screen shots at the command line. The command is fbgrab screenshot.png ; again, this assumes you

have set up the framebuffer. Likely, you do not want to grab a picture of the screen shot tool itself, so type

$ fbgrab -s 5 screenshot.png

and then press Ctrl+Alt+F4 to switch to another terminal. Make sure the application you want to grab is

running; you can replace the 4 with another terminal number as needed. Wait a couple of seconds, and when

the 5 seconds ( -s 5 ) have elapsed, you can return to the original terminal to check the screen shot. The FBGrab

man page also tells you how to produce the best possible size and quality images.

Image Artistry

People are rarely happy with just looking at images: In many cases, you will need to convert an image to

another format. If you want to edit an image, you can install the ImageMagick package, which includes

programs such as Convert, Identify, and Import [4].

To discover the size and color depth of an existing image, type identify image.png (Figure 2). This works with

multiple images, too; the command is identify *.png , in this case. To convert PNG images to JPEG, just type

$ convert image.png image.jpg

Figure 2: The identify command shows you the properties of an image - its size, format, and color depth.

You might need to produce preview images (thumbnails) for a website. If Konqueror is not available to you

for reducing images, you can combine the Convert command with a call to Resize:

$ convert -resize 200x200! image.

png image_small.png

This creates a 200x200-pixel copy of the original ( image.png ). If you leave out the exclamation mark ( ! ), the

command will just reduce one side of the image to the required size while automatically retaining the aspect,

which prevents distorted thumbnails.

Console Blues

The console is as musically gifted as any GUI: To play a normal music CD, all you need is a tool called Cdcd,

which you can launch by typing cdcd , and which you can control via text input. The tool will ask you where

your CD-ROM drive is (typically /dev/cdrom ) and then display a prompt. Press ? to tell Cdcd to list the

control commands. If you then type rndplay , the software will play the tracks on the CD in random order.

Typing stop quits the player.

Easy Conversions

If you borrowed the CD, you will have to give it back some time. To create a private copy - and I'll assume

you are allowed to do so in this case - just run MP3c. The software converts tracks from CDs to MP3 or OGG

format and also includes a CLI (Command-Line Interface), which gives you keyboard-based controls. Typing

./mp3c launches MP3c; the converted data is dropped into the directory in which you launched the tool.

When launched, MP3c looks for a hidden .cddb folder and asks you whether it should create a folder if one

does not exist. Pressing the Tab key moves the cursor to YES ; then press Enter. Alternatively, the arrow keys

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move the cursor. By default, MP3c assumes that your CD-ROM or DVD drive is in /dev/cdrom , although this

might not be the case. If not, press F2 and type the correct path to your drive. F2 takes you to the MP3c

configuration menu, in which you can change many settings. Enter opens the fields for editing.

As an example, the software typically saves titles in files that use cryptic numbers as names. If you change the

pattern in Pattern for MP3/OGG filenames to [%1 - %2.mp3] , the software will write the artist name followed

by the title of the track.

Despite the prefix, which would suggest otherwise, MP3c creates OGG files by default. Moving the cursor to

the bottom of the configuration menu and selecting Load Presets (MP3/Lame) tells MP3c to create MP3s, as

the name would suggest. However, this means modifying a couple of other options, and then saving your

changes by executing Save Configuration . Don't forget to save if you want to keep the changes when you

restart the program.

The left side of the MP3c CLI lists the names of the individual tracks on the music CD (Figure 3). Pressing F4

encodes a single track; F3 encodes the whole CD. Q quits the individual menus and then the program. To

discover what other options MP3c offers, you can either work your way through them or press H for help.

Figure 3: MP3c lets you rip the tracks on a music CD and convert them to MP3 or OGG format.

Do-it-Yourself CDs

Many CD players will detect and play files in OGG and MP3 format without any trouble. To be on the safe

side, you might want to convert the songs for your CD to WAV files. Cdparanoia is a useful tool for this [5].

A simple command is all it takes, but make sure you have enough disk space. The cdparanoia -vsQ command

tells you the number of tracks on the CD. To convert the first two tracks to WAV format for test purposes, for

example, try the command:

$ cdparanoia -w 1-2 -B

If things work out and you would like to convert the whole CD, just leave out the -w 1-2 parameter (Figure 4).

To keep the software from storing all the tracks in a single file, set the -B option. Unfortunately, the tool will

not keep the track names; instead, it renames them to something generic, like track1.cdda.wav,

track2.cdda.wav , and so forth. Some manual processing is needed.

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Figure 4: Cdparanoia is used whenever you need to copy the songs from one music CD to another but don't

have a second drive.

Nice Cover!

The tiny Disc Cover program will create a simple but workable cover for your CD [6]. To do so, it retrieves

the data for the individual tracks from CDDB, assuming there is an entry for the CD in question. You can

decide which text format to use for the cover. A typical command is:

$ disc-cover -t pdf -D /dev/scd0

The tool searches for the drive with the CD in /dev/cdrom , but setting the -D option specifies an alternative

path. The -t option sets the required output format - PDF in this case. Alternatively, you can create covers

formatted in PS, DVI, HTML, or TEX. The more parameters you pass in to the software, the more you change

the cover. If you are using a slim CD case, you additionally need to set the -c slim flag. The -pic image.jpg

command lets you add an image file to the cover.

Video Editor

The Streamripper tool can rip a stream at the command line [7]. The command

$ streamripper http://85.25.145.

179/motorfm.mp3.m3u

drops the stream into a single, huge file. The recordnplay.sh script lets you play back the sound you recorded:

streamripper http://85.25.145.17

9/motorfm.mp3.m3u -r &

sleep 20

mplayer -cache 500 'http://local

host:8000'

Typing chmod u+x recordnplay.sh makes the script executable, then launch the script (Figure 5). The first

command tells Streamripper to record the stream, and the -r option tells the program to publish the stream at

the same time via port 8000.

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