Succesive bitrate conversions

[Edua]

Sorry for this perhaps naive question. I have a number of tracks in my computer (SS Library) from a CD saved in ATRAC3+ 192 kbps. I can transfer them to my device using that resolution "as is" or choosing a different one.

Now it seems fairly evident that even if I chose a HIGHER bitrate at that point, I'm not going to get closer to the quality of the original CD.

But what happens if you go for a LOWER bitrate? What I mean is: will you get an even lower audio quality because of the "re-conversion" involved than if you had directly used that lower resolution to begin with?

Thanks a lot for any answers.

[Kardon]

Sorry for this perhaps naive question. I have a number of tracks in my computer (SS Library) from a CD saved in ATRAC3+ 192 kbps. I can transfer them to my device using that resolution "as is" or choosing a different one.

Now it seems fairly evident that even if I chose a HIGHER bitrate at that point, I'm not going to get closer to the quality of the original CD.

But what happens if you go for a LOWER bitrate? What I mean is: will you get an even lower audio quality because of the "re-conversion" involved than if you had directly used that lower resolution to begin with?

Thanks a lot for any answers.

I believe any artifacts that the initial 192kbps encoding introduced will be present, and further enhanced and more artifacts will be created. You would be best off re-encoding the file from its original state down to a lower bitrate.

Edited August 31, 2008 by Kardon

[sfbp]

The only upconversion thought to be safe is 292kbps (Atrac SP) to 1411Khz (PCM/WAV). This is because Atrac was specifically designed to do this.

Since your tracks off CD started out as 1411, I suggest you get them from the CD again. It seems common ground that for *most purposes* 256 is "good enough" for the HiMD format. (some purists insist on PCM, but if you can't tell, then why worry?).

[greenmachine]

It depends on difference between initial and final bitrate. 256 to 64 won't be much different from directly encoding to 64, but from 192 to 128 or 128 to 96 for example could be significantly inferior to directly encoding to the final bitrate. How noticeable these artifacts are, depends on your hearing. Why not give it a try with some test encodings?

[culp4684]

Very interesting question...

I have over 70 GB in my SS library and a lot was saved at 352 kbps. I've often downconverted to 256 kbps and notice no difference in similar CD recordings transferred directly to that bit rate. I'm thinking it's all Atrac, so why should there be any quality loss at the same rates? Now if you were going from MP3 to Atrac, that's a whole different story...

[Edua]

A belated thanks guys... interesting answers. I converted some tracks to 64 kbps and some to 135kbps (ATRAC 3). The results are very good in both cases, perhaps a little better in ATRAC3, but sometimes it's hard to tell between 64, 135 and 192 kbps. Could this be because the original recording (which I won't get hold of very easily) dates back from the early sixties? (I mean the source is not extremely good quality soundwise)

[greenmachine]

There are several factors. The quality of the recording, the quality of your playback gear (headphones, loudspeakers), the playback environment as well as how critical you are listening will influence your minimum required quality. What sounds acceptable to you at the moment may not sound good enough with any of these factors changing.