The quantum of WAV file is a square wave. What is the quantum of a WMA file?
Audio Artifacts: WAV vs. WMA
Started by ●May 28, 2004
Reply by ●May 29, 20042004-05-29
Curious wrote:> The quantum of WAV file is a square wave...Where did that strange idea come from? For file formats, check out http://www.wotsit.org/ and http://sox.sourceforge.net/AudioFormats.html. What you don't know doesn't hurt much. The major trouble comes from the the falsehoods you believe. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●May 29, 20042004-05-29
Curious wrote:> > The quantum of WAV file is a square wave.No, the quantum of a WAV files is the unit impulse.> What is the quantum of a WMA file?WMA files decode to PCM audio which is what you have in standard WAV files. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ A good debugger is no substitue for a good test suite.
Reply by ●May 29, 20042004-05-29
Erik de Castro Lopo <nospam@mega-nerd.com> wrote in message news:<40B87FC9.D845A077@mega-nerd.com>...> Curious wrote: > > > > The quantum of WAV file is a square wave. > > No, the quantum of a WAV files is the unit impulse. > > > What is the quantum of a WMA file? > > WMA files decode to PCM audio which is what you have in standard > WAV files. > > ErikLow-bitrate WMA files have a pleasant type of distortion to them. Couldn't say the same about low-bitrate WAV files. WMA "noise" tends to be musical while WAV "noise" tends to resemble square-waves. I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to where it is just recognizable by WMA file, and then amplifying it back to normal. The arftifacts are kinda interesting there.
Reply by ●May 30, 20042004-05-30
Curious wrote:> > Low-bitrate WMA files have a pleasant type of distortion to them. > Couldn't say the same about low-bitrate WAV files. > > WMA "noise" tends to be musical while WAV "noise" tends to resemble > square-waves.??????????????> I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to > where it is just recognizable by WMA file, and then amplifying it back > to normal. The arftifacts are kinda interesting there.The artifacts are are result of the lossy encoding method used by WMA files. No fruitful comparison can be made between the lossy encoding of WMA and low bit rate PCM. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ A good debugger is no substitue for a good test suite.
Reply by ●May 30, 20042004-05-30
Erik de Castro Lopo <nospam@mega-nerd.com> wrote in message news:<40B953D6.74D5380A@mega-nerd.com>...> Curious wrote: > > > > Low-bitrate WMA files have a pleasant type of distortion to them. > > Couldn't say the same about low-bitrate WAV files. > > > > WMA "noise" tends to be musical while WAV "noise" tends to resemble > > square-waves. > > ?????????????? > > > I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to > > where it is just recognizable by WMA file, and then amplifying it back > > to normal. The arftifacts are kinda interesting there. > > The artifacts are are result of the lossy encoding method used by WMA > files. No fruitful comparison can be made between the lossy encoding > of WMA and low bit rate PCM. > > ErikWhere -- on the internet -- can I find technical information on WMA compression? Most websites that discuss audio compression talk about MPEG, AC-97 and other types of compression. They get very little -- if at all -- into WMAs.
Reply by ●June 1, 20042004-06-01
Jerry Avins wrote:> Curious wrote: > >> The quantum of WAV file is a square wave... > > Where did that strange idea come from? For file formats, check out > http://www.wotsit.org/ and http://sox.sourceforge.net/AudioFormats.html. > > What you don't know doesn't hurt much. The major trouble comes from the > the falsehoods you believe. > > JerryI think Radium may be back. Jim A.
Reply by ●June 1, 20042004-06-01
WMA is part of Microsoft's .ASF family. The encoding/decoding algoritms are concidered "secret" and are known to Microsoft employees only. I bet you'll find more information about MPEG encoding. This information is considered free for non-commercial use. What do you want to achieve with WMA encoding, anyway? You better take a look at AACplus. That rocks your socks of when it comes to compression on lower bitrates. Best regards, Rob "Curious" <curious11112001@yahoo.com> wrote in message news:34a4f456.0405300857.24e2021f@posting.google.com...> Erik de Castro Lopo <nospam@mega-nerd.com> wrote in messagenews:<40B953D6.74D5380A@mega-nerd.com>...> > Curious wrote: > > > > > > Low-bitrate WMA files have a pleasant type of distortion to them. > > > Couldn't say the same about low-bitrate WAV files. > > > > > > WMA "noise" tends to be musical while WAV "noise" tends to resemble > > > square-waves. > > > > ?????????????? > > > > > I tried encoding to 32 KBPS, 44.1 KHz, mono, decreasing volume to > > > where it is just recognizable by WMA file, and then amplifying it back > > > to normal. The arftifacts are kinda interesting there. > > > > The artifacts are are result of the lossy encoding method used by WMA > > files. No fruitful comparison can be made between the lossy encoding > > of WMA and low bit rate PCM. > > > > Erik > > Where -- on the internet -- can I find technical information on WMA > compression? > > Most websites that discuss audio compression talk about MPEG, AC-97 > and other types of compression. They get very little -- if at all -- > into WMAs.
Reply by ●June 21, 20042004-06-21
Erik de Castro Lopo <nospam@mega-nerd.com> wrote in message news:<40B87FC9.D845A077@mega-nerd.com>...> Curious wrote: > > > > The quantum of WAV file is a square wave. > > No, the quantum of a WAV files is the unit impulse.What does the waveform of a "unit impulse" look like on a graph? Is this the same as the "impulse wave" on the NCH tone generator software? For NCH info: http://www.nch.com.au/tonegen/> > What is the quantum of a WMA file? > > WMA files decode to PCM audio which is what you have in standard > WAV files. > > ErikWhat the WMA-equivalent of this "unit impulse" and what does it look like on a graph? What interests me is why "WMA noise" consist of pleasant tones while "WAV noise" just plain boring noise. What in WMA is responsible for the tones? I have Adobe Audition 1.0. I generate a silent file. I save it as WMA 20 kbps, 44.1 KHz, mono. I convert file this to WAV and then back to WMA several times. I make my last conversion to WMA and save it. I then open this WMA file. Finally I increase the volume of the audio in the WMA file and play. Intrigueing tones result. These tones are typical in low bit-rate, high-sample rate WMA files. If anyone has a valid email address I can send them a WMA file with the characteristics I am talking about.
Reply by ●June 22, 20042004-06-22
Curious wrote:> > Erik de Castro Lopo <nospam@mega-nerd.com> wrote in message news:<40B87FC9.D845A077@mega-nerd.com>... > > Curious wrote: > > > > > > The quantum of WAV file is a square wave. > > > > No, the quantum of a WAV files is the unit impulse. > > What does the waveform of a "unit impulse" look like on a graph?ASCII art (ie only make sense with fixed width font): . zero ................. ..................... which each '.' is a time domain sample.> Is this the same as the "impulse wave" on the NCH tone generator > software?Probably. "Unit impulse" is a standard DSP term.> What the WMA-equivalent of this "unit impulse" and what does it look > like on a graph?No idea. Maybe you should generate an impuse, encode it as WMA and then decode it back to WAV.> What interests me is why "WMA noise" consist of pleasant tones while > "WAV noise" just plain boring noise. What in WMA is responsible for > the tones?WMA is a "perceptual encoder". It analyses audio, figures out where the tones are and which tones are most important to the perceieved sound and then stores these while throwing away the reset.> I have Adobe Audition 1.0. I generate a silent file. I save it as WMA > 20 kbps, 44.1 KHz, mono. I convert file this to WAV and then back to > WMA several times. I make my last conversion to WMA and save it. I > then open this WMA file. Finally I increase the volume of the audio in > the WMA file and play. Intrigueing tones result. These tones are > typical in low bit-rate, high-sample rate WMA files.Considering how a perceptual encoder works, I do not find this suprising. I would expect similar results with MP3 and Ogg Vorbis codecs.> If anyone has a valid email address I can send them a WMA file with > the characteristics I am talking about.My email address is valid, but please do not send me a file. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ "When your hammer is C++, everything begins to look like a thumb." -- Steve Haflich, in comp.lang.c++
