Advertisment

What after MP3?

author-image
PCQ Bureau
New Update

The need for a better compression algorithm arises from limited bandwidth availability over the Internet and limited amounts of expensive Flash memory in portable entertainment devices like MP3 players. Two formats–mp3PRO and Ogg

Vorbis–are making news in this area.

Advertisment

The mp3PRO edge

mp3PRO–the supposed next generation of MP3–launched by Thomson Multimedia on June 14, 2001 claims ‘dramatic improvements in compression rate and

audio quality’. Let’s see how it does that.

The mp3PRO encoder splits the audio data into two parts. One part analyzes the data in the low-frequency band and encodes it into a ‘normal’ MP3 stream so that the final file is backward compatible with existing MP3 players. The second part analyzes the data in the high-frequency band and encodes it. While an existing player will tap into the ‘normal’ stream, an mp3PRO player (decoder) also decodes the second stream, and combines the two to give better sound quality. Hence, music tracks can be encoded at lower bit-rates, which reduces the file size, while still retaining good quality. For example, a WAV file encoded at 128 kbps, 44.1 kHz into a standard MP3 will sound similar to a mp3PRO file encoded at 64 kbps, 44.1 kHz.

Advertisment

The Ogg arrives

Close on the heels of this launch was another–an open-source one this time–Ogg Vorbis. Though not a very popular format when it comes to music sharing or storage, Ogg has been around for quite some time in beta stages for Unix/ Linux, Windows, and Macintosh platforms. Ogg developers announced the launch of the first version (Release Candidate 1) of their software on June17, 2001. Ogg doesn’t claim to have enhanced compression compared to MP3, but offers a music format that gives distributors and developers good audio quality and no patent royalties.

Do they deliver?

Advertisment

We ran a series of tests, which looked at file sizes, time required for encoding, effects of bit-rates and sampling frequencies and the sound quality.

We used a standard 38.7 MB, 16-bit, stereo, signed WAV file for encoding. We were also working under some limitations. The mp3PRO encoder being a demo release, currently encodes files at 64 kbps and 44 kHz only. Also, the Ogg encoder encodes files at a lowest bit-rate of only 128 kbps. Here is a summary of the results as shown in table.

Advertisment

Keeping the sampling frequency base same (at 44 kHz), an MP3 file encoded at 64 kbps had the same size as an mp3PRO file. However, the sound quality was as good as an MP3 encoded at 128 kbps, which effectively takes up twice the file size. Time taken for the encoding is a little more however (2:31 as against 2:15). The RCA mp3PRO player is CPU-intensive with about double the CPU usage than

Winamp.

For the Ogg format file, the file size was almost similar to the MP3 (128 kbps, 44 kHz). But the time taken for encoding was significantly longer. During the playback of the Ogg file, there was a minor VBR (Variable Bit-Rate) in the final file. Instead of a constant 128 kbps, the file showed a variation from 124 to 132 kbps. This may sometimes result in a smaller file size than an MP3 (for instance, in case of tracks with more ‘silence’).

Ashish Sharma

Advertisment