AAC + iTunes
- Thread starter ristin_uk
- Start date
).it wouldn't be totally meaningless for compressed formats - it would give in indication of quality (and would presumably be dependant on samping frequency and numbers of bits used in sampling). This is how you would compare the quality of two seperate compression techniques.
R.
R.
Compression is what turns a Mb/s CD audio stream into a kb/s mp3/aac audio stream.
For each (say) second of uncompressed audio stream (about 1.4Mbits worth), the encoder has (say) 128kbits to describe the original signal. It will keep adding detail until all 128kbits have been used.
A good encoder will be able to more accurately describe the original audio bitstream for a given encoded bitrate (or encode to a similar standard using a lower bitrate).
(Then there are Variable Bitrate Encoders that can choose to use more or less bits to encode depending on the complexity of the incoming bitstream.)
As for the question of whether the iPod supports AAC - there's no mention of it I can find on the Portal Player website, but I do know that AAC codecs exist for the ARM processor that the iPod mp3 device is based on...
Jim
For each (say) second of uncompressed audio stream (about 1.4Mbits worth), the encoder has (say) 128kbits to describe the original signal. It will keep adding detail until all 128kbits have been used.
A good encoder will be able to more accurately describe the original audio bitstream for a given encoded bitrate (or encode to a similar standard using a lower bitrate).
(Then there are Variable Bitrate Encoders that can choose to use more or less bits to encode depending on the complexity of the incoming bitstream.)
As for the question of whether the iPod supports AAC - there's no mention of it I can find on the Portal Player website, but I do know that AAC codecs exist for the ARM processor that the iPod mp3 device is based on...
Jim
illl prove this by encodeing a ogg file and then re-encoding the same file with the same software at the same kbps in mp3, the ogg file will be much smaller then the mp3.
jeb1138
Carioca
Poptart's idea sounded good. Why only theorize when you can experiment? Here are the results of encoding "No Such Thing" by John Mayer in AAC (MP4, via quicktime) and MP3 (via iTunes) both at 64kbps:
The numbers are slightly off, but you have to remember that the file doesn't only hold music, it holds track names and a few other very small things (like the extra baggage the AAC (MP4) file had by being wrapped up inside what could potentially be a movie file). And still the files were within about 2% of each other's sizes. The filesize at a given bitrate is the same no matter what the codec.
I tried the same experiment on my brother's PC with Real's RealJukebox using their mp3 encoder and their proprietary encoder and then with Windows Media Player using Microsofts proprietary encoder. All 3 were done at 64kbps per second and all 3 were the same file size (approximately) as the 2 files I got on my mac. Crossplatform, crossplayer, crosscodec -- a given bitrate yields the same filesize every time.
After listening to the MP3 and AAC files with a pair of Sennheiser HD590 headphones, I can definitely say that the AAC file sounded much better than the MP3 file. Very nearly (but not quite) as good as a 128kbps MP3 I made of the same song.
AAC will save you space because you will be able to record at a lower bitrate, not because the bitrates will yield smaller file sizes. The bitrate in the music-ripping world is defined as the rate at which bits are stored on your harddrive -- the bits of harddrive space per second -- after compression, like ladavacm said. If 'ogg' defines bitrate differently then I have no idea how they are defining it and it seems like that would be a rather confusing thing to do.
Anyway, it was a fun experiment. Whaddya'll think?
The numbers are slightly off, but you have to remember that the file doesn't only hold music, it holds track names and a few other very small things (like the extra baggage the AAC (MP4) file had by being wrapped up inside what could potentially be a movie file). And still the files were within about 2% of each other's sizes. The filesize at a given bitrate is the same no matter what the codec.
I tried the same experiment on my brother's PC with Real's RealJukebox using their mp3 encoder and their proprietary encoder and then with Windows Media Player using Microsofts proprietary encoder. All 3 were done at 64kbps per second and all 3 were the same file size (approximately) as the 2 files I got on my mac. Crossplatform, crossplayer, crosscodec -- a given bitrate yields the same filesize every time.
After listening to the MP3 and AAC files with a pair of Sennheiser HD590 headphones, I can definitely say that the AAC file sounded much better than the MP3 file. Very nearly (but not quite) as good as a 128kbps MP3 I made of the same song.
AAC will save you space because you will be able to record at a lower bitrate, not because the bitrates will yield smaller file sizes. The bitrate in the music-ripping world is defined as the rate at which bits are stored on your harddrive -- the bits of harddrive space per second -- after compression, like ladavacm said. If 'ogg' defines bitrate differently then I have no idea how they are defining it and it seems like that would be a rather confusing thing to do.
Anyway, it was a fun experiment. Whaddya'll think?
The Ogg Vorbis algorithm is inherently variable bit rate.
Instead of specifying a bitrate to encode at, you specify a "quality setting" that approximates the quality of certain mp3 encoding bitrates, but with smaller file sizes. Eg. A quality setting of "4.99" results in quality close to that of encoding with mp3 at 192kbps, but with a 30% smaller result.
See <URL>http://www.vorbis.com/intro.html</URL>
Jim