From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Benno Senoner" Date: Tue, 20 Jun 2000 11:54:03 +0000 Subject: Re: [linux-audio-dev] Re: Multimedia compression Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org On Mon, 19 Jun 2000, Juhana Sadeharju wrote: > >From: Benno Senoner > > > >I prefer to use MPEG Layer 2 ( MP2) at 384kbit (lossy) which outperforms all > >MP3 based codecs even 320kbit. > > How do you know it? Where I could read tests about it? > I have used layer 3 with 320 kbps for compressing radio and cassette > recordings (both music and sound samples snipped from them), so, most > probably I have used the right compressor. But is layer 3 with 320 kbps > somehow not enough for studio mikes (voice, guitar, etc.) or for digital > synth tracks? > > Of course, for compressing the final mix (20-bit or greater) of studio work, > the 16-bit MP3 is not enough. But 16-bit could be enough for individual > sounds, vocals, etc. However, I would not use any MP3 compression for even > those because I would record only with 20-bit A/Ds in studio. I have used > MP3 only because I have nothing better than 16-bit A/Ds. So, what compressor > I could use for 20- or 24-bit material? Should we look at ourself for > 20- or 24-bit compressor or can MP3 or AAC handle them (similarly than JPEG > can handle 16-bit/channel images)? I think Philips MPEGLIB can encode 24bit files, their MP2 software encoder is the same used in DMX SAT radio encoders , and other DSP platform. I say I would prefer MP2 over MP3, because MP3 *WAS DESIGNED* for lower bitrates. ( 128-192kbit). Plus consider the fact that MP2 has better random-seek properties (no long frame dependencies), not to mention higher speed when encoding/decoding material. If you ask me, if I were designing a system with the best possible audio quality while achieving 1:4 compression I would chose MP2 or alternatively APT-X ( http://www.aptx.com/ ) Unfortunately APT-X is not available as a software-only CODEC, it is used in some cinema audio systems (DTS) , and doesn't use perceptual coding, and has an amazing 2.9ms codec delay at 44.1kHz. The granularity of editable regions is 80usecs = 2 samples, that means you can edit an APT-X file with almost the same precision as a PCM file. ATPX is some kind of ADPCM but which encodes subbands with different precision to reflect the frequency resolution of the ear. > Note that 16-bit is most probably enough for mic recordings, but the > extra bits are needed for having extra room. I would not want to dither > 20-bit recording down to 16-bit even it would fit very well. > > Juhana But I guess you are looking at a totally free codec :-) therefore there is only MP3 , ISO MP2 encoder and perhaps a good VORBIS (the patent-free audio codec which matches MP3 quality) Benno.