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Can I encode MP3@lower bitrate than usual b/c itís from a smaller WMA?, Was: Converting WMA to MP3 at what bitrate?
musicollector
post Oct 26 2011, 03:53
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I normally create MP3s at 320 kbps. However, I have a bunch of WMA files which I want to convert to MP3. Does it make a difference if I convert to, say 120 kbps, as opposed to 320 kbps? Is there a bottleneck effect in that WMA files may be at a lower bitrate, consequently, encoding at 320 not making that much of a difference from doing so at a lower rate?

TIA.

Harry

This post has been edited by db1989: Oct 26 2011, 12:20
Reason for edit: removing unrelated link to personal site


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db1989
post Oct 26 2011, 15:28
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Transcoding from one lossy format to another will always cause further degradation of quality; this is not invariably audible, but its being so is fairly likely at bitrates such as 128 kbps and in formats such as WMA and MP3, especially in succession. By the same token, any given lossy encoder has no way of knowing that the signal it is processing has previously been encoded at all, whether that be at a lower bitrate, by the same or a different format, etc., so there are no smart tricks that enable maximal preservation of quality or suchlike.

Both of these phenomena undermine what might initially seem like the intuitive reasoning that one should not encode to a higher bitrate. Ideally, avoid transcoding whenever possible. But assuming that’s not an option, the simplest course of action is just to encode at 320 kbps as normal.

I had a quick search (use the built-in Google bar, or the IPB search with + prepended to each word) for previous discussions about converting WMA to MP3 and found at least one thread that might be of interest to you; I dare say there are more about those specific formats or about lossy–lossy transcoding in general.

This post has been edited by db1989: Oct 26 2011, 15:34
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musicollector
post Oct 26 2011, 21:29
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HI db1989,

You have more than adequately answered my question. Moreover, the link you provided is a gold mine! THANK YOU!

I will follow some of the ideas suggested in the other thread, such as A-B (WMA/MP3)comparisons at various bit rates. Until then, I will simply convert to 320 kbps and keep the original WMA files. After all, hard drive space is cheap. If it is lossless to lossless, I did not notice it when I played the converted 320 kbps MP3 files trhough my high quality headphones. Sounded pretty good to me, though I am not a 12-year-old girl who has never listened to loud music before or a dog. smile.gif The problem is that I canot play WMA files on my iPod, meaning I have absolutely no choice.

Now, one other question remains. Would a VBR bitrate be better than 320?

This post has been edited by db1989: Oct 27 2011, 16:29
Reason for edit: deleting pointless full quote of last post


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db1989
post Oct 27 2011, 16:43
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Glad to help!

QUOTE
Would a VBR bitrate be better than 320?

If you were encoding for the first time, probably yes: then, the encoder could avoid wasting bits on simpler regions of audio and (via the bit reservoir) save them for more complex passages. There are also several gold-mines of this variety around, too. smile.gif You may well want to look into using a VBR setting such as -V0 or even lower instead of -b320 for your normal encodes.

As to transcodes… With a stream that’s already been through one round of lossy encoding, which compared to its source may be of lower perceptual quality and yet increased mathematical complexity from the vantage-point of the second encoder (e.g. as added noise), the question’s more difficult; extra bits may be wasted on noise, etc. I don’t know and also am unsure if there can be a definitive answer. Anyone?? tongue.gif

I certainly wouldn’t shift from -b320 for transcodes if you continue to use it for original encodes; it’d be breaking uniformity and increasing the likelihood of audible artifacts due to the signal already having been encoded before. It might even be fairly safe to use a lower (e.g. VBR) setting on all of your files…but here I should stop my supposition and let someone else answer!

This post has been edited by db1989: Oct 27 2011, 16:45
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musicollector
post Nov 26 2011, 19:14
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Thanks. I have been doing this for several weeks. The WMA's are all at 192 kbps which I am converting to 320 kbps. Correct me if I am wrong, but my feeling on this is that though the MP3 result may not be "better" than the original WMA, the fidelity will be preserved more faithfully using a 320 transcode rate. It won't be any better but it will be closer to the original at 320 than if I transcoded from 192 WMA to 192 MP3. Does that make sense?

This post has been edited by db1989: Nov 26 2011, 19:28
Reason for edit: removing unnecessary full quote of above post


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db1989
post Nov 26 2011, 19:32
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Yes, transcoding to a higher bitrate should result in relatively less degradation of the signal and thus a lower likelihood of (additional) artefacts being introduced.
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musicollector
post Nov 26 2011, 19:49
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QUOTE (db1989 @ Nov 26 2011, 11:32) *
Yes, transcoding to a higher bitrate should result in relatively less degradation of the signal and thus a lower likelihood of (additional) artefacts being introduced.


Thanks again for all your advice. I have decided to go with 320 for all transcoding.


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