GTranscode

Transcoding is the process of converting a audio or video file (or group of files) from one media format to another. On Linux one of the most powerful applications for doing this is Transcode which is an application you use on the command line. GTranscode is a graphical user interface (GUI) for the Transcode command line application. GTranscode makes it easier to use the functionality of Transcode for those not acustomed to using command line interfaces (CLI) or for those new to the practice of transcoding.

Installing GTranscode

To use GTranscode you will first need to install Transcode. Once this is complete you can continue continue through the following steps.

Debian and Ubuntu

Installation under these two platforms is very easy. Infact you don't need to have Transcode installed beforehand as the Package Management Systems of these two vareities of Linux will install Transcode as part of the GTranscode installation process. To install both applications you will need be online (connected to the net) and type the following command in terminal (on the command line):

sudo apt-get install gtranscode

Thats about as simple as it can get. You type the command and then the apt-get command will find the correct files online, download them, configure them, and install them. Not only that, the apt-get application also gets all the files and libraries that Gtranscode depends on including the files for Transcode.

Gentoo

To install on Gentoo you use the inbuilt Package Management System which is know as emerge. Unfortunately at this time there is not a Gentoo package for GTranscode so you will need to install it from source.

Redhat

To use the Redhat Package Manager you will need to find and download the appropriate rpm files. However at the time of writing there are no such files available for GTranscode and you will need to install from source.

Installing from Source

At the time of writing the current version of GTranscode is gtranscode-v0.3

The downloaded source files are therefore gtranscode-v0.3.tar.gz To start the installation process you must first have open a terminal, and locate the directory that contains the downloaded file. You must use the cd command to navigate to the correct directory, or alternatively you can copy or move the files (using the cp or mv commands) to your current working directory. If you don't know how to do this then please first read up on how to change directories in Linux and probably it is a good idea to also learn somehting of the Linux file structure and common basic commands. To check the files are actually in the same directory as your terminal you will need to use the ls (list) command by typing this command directly into a terminal and pressing return. If the files are there you will see them listed in the output of your terminal like so:

The output of the above terminal shows a list of files in the directory I am currently working in. The file gtranscode-v0.3.tar.gz is listed on the left most column near the bottom. This is a good sign. If you don't see it then you will have to locate it in the directory you downloaded it to.

Decompress the Files

Now you will need to unpack (decompress) the file you have just downloaded. To do this use the tar command like so:

tar zxvf gtranscode-v0.3.tar.gz

If all is well your terminal will output something similar to this:

gtranscode/
gtranscode/TODO
gtranscode/interface.c
gtranscode/interface.h
gtranscode/Makefile
gtranscode/LICENSE
gtranscode/README
gtranscode/tcprobe.c
gtranscode/tcprobe.h
gtranscode/CHANGELOG
gtranscode/main.c
gtranscode/transcode.c
gtranscode/transcode.h

The above files are source files and you use these to install the applicaiton. Use the cd command to change directories to gtranscode :

cd gtranscode

Checking the README

It is at least polite and probably good practice to read the README included any source code. This file can save you a lot of problems if well written. Often source files also come with a INSTALL file which contains information on how to install your software. In this case there is no such file so reading the README will have to do. Open it up wiht your favourite text editor. If you don't have one then you will need to read something about how to open, read, and edit text files in Linux. You can't get very far without this knowledge. In the meantime you could try one of these commands:

less README

vi README

nano README

soffice README

Hope fully one of them will open a text edito for you and you can read the content of the file. The file doesn't say a lot (which isn't necessarily a bad thing). It does state two important things:

Requires
------------------------------------------------------------------------------
- transcode (which comes with tcprobe) 
from http://www.Theorie.Physik.UNI-Goettingen.DE/~ostreich/transcode/
- GTK+ 1.2 (which should come with gtk-config)

This means you require Transcode to be installed before you can install GTranscode. Additionally you will need GTK+ 1.2 which is probably installed on your operating system. To check if this software is installed type this:

gtk-config --version

you should see something like this:

eset@focus:~$ gtk-config --version
1.2.10
eset@focus:~$

The above feedback shows that GTK+ is installed and it is version 1.2.10, because this is a version greater than GTK+ 1.2 we are ok. If you do not see any feedback in the terminal or you get an error message (eg. command not found), or the version installed is less than 1.2 then you need to find a version of the GTK+ software which is 1.2 or greater and install it.

You should also check to see if transcode is installed type:

 transcode --version

If it is there you will see some feedback like this:

transcode v0.6.14 (C) 2001-2003 Thomas Oestreich, 2003-2004 T. Bitterberg

If you get a command not found error then Transcode is not installed and you first need to go through this process.

The second inportant piece of information on the README is a tip on how to install the application. The author states:

Installation:
------------------------------------------------------------------------------
make
cp gtranscode /usr/bin

This is good information. Essentially its saying that the installation should be simple.

Make

Lets try the author on their word. Type the make command in the temrinal and hit return. If you see the following then the application has been built:

gcc -g  `gtk-config --libs` `gtk-config --cflags` main.c 
tcprobe.c interface.c transcode.c -o gtranscode

Testing

Before moving the newly compiled software to the bin directory as the README suggests, lets test the application to see if there are any problems. Try this:

 
./gtranscode

If the result of the above command is the following then GTranscode is installed:

Moving GTranscode to bin

Most programs (software) on Linux is stored in the bin directory which is found at /usr/b in to copy the application to this location type the following in the command line:

mv gtranscode /usr/bin

You might bot be able to do this if you don't have the right permissions, in which case either the system administrator has to do this for you or you can try this command :

sudo mv gtranscode /usr/bin

Whichever way you use to move the file you should now be able to execute it (start it) by simply typing :

gtranscode

GTranscode Interface

Its a pretty simple interface hiding a lot of powerful possibilities.

The main components of the software interface is the Input area on the left, and the Output area on the right.

Input Area

This is the section that determines what file(s) you choose to transcode (convert).

File Selector

To choose a file or directory for transcoding you simply click on the Browse button next to Video File or Directory and this will open a file browser :

Of course you can Create Directories, Delete Files, and Rename Files with this interface but mainly you want to use it for choosing the files you wish to transcode. When you have browsed to the file you wish to convert into another format simply highlight it by clicking on the file name and press OK. If you wish to transcode an entire driectory then open theat directory by double-clicking on the name in the file browser, then do not select a file name, just press OK.

When you have selected the directory of file for transcoding you will see some feedback about your selection on the middle of the GTranscode input area:

The above is the feedback for a single file. If you have loaded a directory the feedback will look somehting like this:

You should always check the feedback to see if you have indeed chosen the right file.

import module

The import module decodes the input file. There are many input modules but it is best to allow the application to try and automatically recognise what the file format is and which module it should use. Do not change the default value "auto (use probed)" unless you experience problems reading the file with the application.

frames

You may decide to transcode only part of a video file. In which case you can enter the beginning frame and the end frame of the section to be transcoded into this field. If you wish to do this then the format would be something like f1-f2 where f1 is the beginning frame and f2 is the end frame. Here is an example:

Output Area

On the right of the interface you will see information and options regarding the type of file or files you would like to create.

Output Video File

The Output Video File is simply the area that you use to browse to the place on your file system where you would like the file(s) to be saved. You must also specify a filename for the transcoded file. If you are not sure of the suffix to be included on the file you don't need to include a file suffix at this point. For example the following would be acceptable:

You can work out the correct suffix later if you need to.

Pass Through vs Full Processing

Also on the right of the interface you can choose between the Pass Through and Full Processing options.

With Full Processing the a/v stream is first decoded then encoded again into a new file. In pass-through mode it's read without decoding and written as is to the output file it's a way to convert formats losslessly.

Generally you will choose Full Processing.

Full Processing Options

If you choose Full Processing you will see a further set of options:

These options define the format of the file that you will create.

Export Module

The export module setting defines the format of the newly created media file. Currently Transcode and hence GTranscode converts to many formats including DivX;-), XviD, DivX 4, DivX 5, AVI, MPEG, raw DV, and others. For a full list please see the Transcode Wiki (http://www.transcoding.org/cgi-bin/transcode?Export_Modules) . Unfortunately GTranscode does not load in a nicely formated drop down menu so you can choose from these formats, instead you have to type the information into the export module field. For example, to transcode to DivX 5 you would type divx5 in the export module text box. Modules you could try typing in to the export module for transcoding video files include:

mpeg2enc
xvid
divx5
mpe1

Additionally you can add other options to the export module you have chosen. To do this you will need to know a few command line options from Transcode into the export module optional string. For basic use of GTranscode this field can be skipped.

frame rate

The frame rate is for setting the number of frames per second for the output (transcoded) file. If you leave this field the frame rate of the input file will be preserved.

deinterlace mode

Interlacing splits a video image into two separate scan lines in a single frame. All analog TV formats use interlaced video. Interlaced video, when viewed on a TV, looks fine but when viewed on a computer the video displays a series of lines across the video. Video files which are interlaced need to be de-interlaced to be displayed correctly on a computer. Transcoding can do this and the output of the de-interlaced video is refered to as progessive or non-interlaced video.

If you wish to de-interlace video then you will need should try the available options, perhaps starting by choosing interpolate scanlines from the available drop down menu.

antialias

The deinterlacing process can generate unwanted artifacts in the video in the form of "jagged" lines. To minimise this distortion you can choose various methods of video anti-aliasing. The anti-aliasing methods do not remove the distortions but disguide them so they are not as apparent. You will only need to experiment with these options if you are deinterlacing video (see above).

video bitrate

This option determines the bitrate of the output (transcoded) file. The bitrate is very important for the final quality of a video file. The higher the bitrate the higher the quality, and the larger the file size. If you are encoding a file for delivery over the internet or you have limited storage space the the bitrate settings become very important. The setting of the bitrate is entirely up to you, however in most circumstances you would not go below 64 kbps. To experiment you could try 100, 200, and 1600 in the field provided.

preserve aspect ratio

If you wish to change the height and width of the output video file then you can use these fields. If you wish to change the size of the video window but manitain the raio of height to width then make sure the box of on the left is press down. If you do this then you can enter either your prefered height and the application will calculate the correct width (or vice versa). You can however elect not to maintain the aspect ratio in which case you may get odd but interesting results.

use YUV

from the Transcode manual page: "This option is depricated. It is default now because it is most codecs' internal format so there is no need for conversions." In other words, don't change this setting unless you know what you are doing.

Swap, flip, mirror

Don't change these options unless you want the output file to be changed dramatically.

Audio Options

This area dictates the audio transcoding output options. You can again choose between Full Processing or Pass-Through options (see above). If you choose Full Processing you get several options:

Full Processing

audio format

Choose here from the drop down box the posisble formats you would like the audio converted too.

audio bitrate

As with the video bitrate this option plays a significant role in determining the quality of the audio and the final file size. Experiment with the values provided.

volume gain

Gain is a way to boost the audio levels. if your audio level (in the original file) is low you may wish to experiment with this value, otherwise leave it set as 1

Command Line Display

To help you learn the syntax for Transcode there is a nice output field at the bottom of GTranscode that displays the command that reflects the options you choose in the interface.

Using GTranscode

There are many ways of using GTranscode so its tricky to show them all, however here is an example of converting a avi file to divx and resizing the aspect ratio, video bitrate, and fps in the transcode.

Open Source File

First we load the correct file by opening GTranscode and pressing Browse :

This will open a file browser and you should select a file to be transcoded :

In this example we will select the caro.avi video :

Select (highlight) the file you want and press OK and you will see the main interface display the information about the file:

Output Settings

Now you will want to choose the format of the outut file.

Choose Output File

You will have to save the final transcoded file somewhere, to do this you will need to enter the path and filename in the Output Video File filed. If you don't know what a path is then just press Browse:

Once you have pressed Browse you will see the file browser again :

Now browse to the directory where you want the transcoded file to be save and write the file name in the bottom field:

Now press OK and the information of your new file name and path should be displayed:

Full Processing Mode

Now press the Full Processing Mode button. You will now see some options from which you can choose which will determine the format of the output file.

We will not be using most of these but we will choose settings for export module, frame rate, video bitrate, and aspect ratio.

Now we will choose the following options:

export module : divx5
frame rate : 12
video bitrate : 64
aspect ratio : 200 x 150

If you fill out these details in the interface ot should look something like this:

Command Line Output

If you look at the bottom of the inteface you will see infomration relating to the command that you would use :

 transcode -i "/home/eset/movies/caro.avi" -P 2 -y divx5 -f 12 -w 64 -Z 200x150 -V 
-o "/home/eset/movies/newfile.divx"

Start Transcoding

Now press go from the File menu :

If all is well you will see somehting like this appear:

When the file is completed its transcoding you can then play it!

License

All chapters copyright of the authors (see below). Unless otherwise stated all chapters in this manual licensed with GNU General Public License version 2

This documentation is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this documentation; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

Authors

_{Free manuals for free software}

General Public License

Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

Preamble

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TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

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NO WARRANTY

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END OF TERMS AND CONDITIONS