Techie-Gyan » audio

VLC media player 0.9.2

Aditya — Tue, 16 Sep 2008 15:59:49 +0000

VLC media player 0.9, code name Grishenko released recently.

Simplified settings and dialogs
Media library integration
Album art displaying and metadata editing
Live activation of Video and audio filters
Basic encoding profiles
Multiple start modes (classic, enhanced and minimalist)
System tray icon and minimizing
Fullscreen controller

According to their wiki following are improvements in Playback:

A lot of new decoders, demuxers, and protocols have been added.

There are new codecs support, like Flash video variants, camcorder codecs (M2TS ones), Dirac, Atrac3, H.264 PAFF, APE audio, RealVideo, VC-3, Fraps and others, but also better decoding and better performance. Many thanks to the FFmpeg project which can take most of the credit for these improvements.

There are improvements in the demuxers and new supports (subtitles format rework with many new formats, Tivo2, OMA, MIDI support…).

Tag supports of audio files have vastly been improved(fix of APE, AAC, OGG tags,…)

This version also supports DVB windows devices (BDA), iSight Webcams, v4l2 on Linux and many other ones.

Other than this one very good improvement which was pointed out by one friend is that you can apply Audio and video filters. One of the audio filter is playing the audio with some offset with video which can fix some of the videos file with existing offset (lip synchronization).

VLC media player 0.9.2 – Grishenko from Antoine Cellerier on Vimeo.

Audio files handling in Java – javax.sound.sampled.AudioSystem

Aditya — Thu, 05 Jun 2008 14:03:48 +0000

Problem: Few days before i wrote a post about converting audio media file to different format using SoX. I also mentioned one limitation of Sox that it does not convert audio file formats and resample it when rates are same in input and output and gives following error:

sox: Input and Output rates must be different to use resample effect

See the solution in the post but that will suit you if you are using Sox manually.

Solution: While using java, You first need to know about specs of audio file before converting it or applying some effects. javax.sound.sampled package solves this problem, which i figured out while solving the problem:

 
AudioFileFormat format =  AudioSystem.getAudioFileFormat(mediaFileToConvert);

Once you get AudioFileFormat from the File, you can get get different specs of Audio file:

 
AudioFormat audioformat = format.getFormat();
/* returns int - Obtains the number of channels.*/
audioformat.getChannels();
/* returns AudioFormat.Encoding - Obtains the type of encoding for sounds in this format.*/
audioformat.getEncoding();
/* returns float Obtains the frame rate in frames per second.*/
audioformat	.getFrameRate();
/* returns int Obtains the frame size in bytes.  */
audioformat	.getFrameSize();
/* returns Object Obtain the property value specified by the key.  */
audioformat.getProperty(String key);
/* returns float Obtains the sample rate.*/
audioformat.getSampleRate();
/* returns int Obtains the size of a sample.  */
audioformat.getSampleSizeInBits()
/* returns boolean Indicates whether the audio data is stored in big-endian or little-endian byte order.  */
audioformat.isBigEndian();

I have noted down very basic use of AudioSystem , I will look more and will write about mixing and conversion using Java soon.

sox: Input and Output rates must be different to use resample effect

Aditya — Sun, 25 May 2008 16:26:54 +0000

Problem: While using SOX for converting audio files in one single format, we faced an issue with SOX. It doesn’t allow resampling of media file if source file sample rate id same as of destincation file e.g. if you are trying to convert media files to Mono Channel, Audio Sample rate 8kHz and Audio sample size 16 bit and if origincal file has same sample rate of 8kHz, SOX gives an error and doesn’t ignore it.

The command for modifying the origincal media file was
'sox foo-in.* -r 8000 -c 1 -s -w foo-out.wav resample -ql'

and error was following:

sox: Input and Output rates must be different to use resample effect

Solution: We need to figure out the sampling rate of audio file and change the command accordingly

Implementation: SOX itself gives details about the input media file using following command

sox -V input.file -e

Use above command for getting details about the sample rate and use command

sox foo-in.* -r 8000 -c 1 -s -w foo-out.wav

for converting your media file and skip the resampling of it is not required i.e. if input and output rates are same.

Convert formats of computer audio files

Aditya — Tue, 20 May 2008 18:49:19 +0000

Problem: We had this sound stack/VoIP stack which was unable to play all format of media files. Reason for this restriction was size of stack and that was our restriction too, we wanted to keep stack size as small as possible and not include codecs in it. This VoIP stack could play a certain format of media file i.e. WAV format, Audio sample size 16 bit and Audio sample rate 8kHz.

This module has to play media files input from a web application which was open for all users. We could not ask all people to convert their media in certain format because generally the end user does not have much technical information up to these details.

Solution: Try to convert all type of media into required format i.e. WAV, 16 bit and 8kHz.

Implementation: After searching on internet we got ‘SOX’ i.e. Sound eXchange, the swiss army knife of sound processing programs. SoX is a command line utility that can convert various formats of computer audio files in to other formats. It can also apply various effects to these sound files during the conversion. As an added bonus, SoX can play and record audio files on several unix-style platforms.

Use following command to convert media into WAV, 16 bit and 8kHz format:

sox foo-in.* -r 8000 -c 1 -s -w foo-out.wav resample -ql

Read more documenation at http://sox.sourceforge.net/