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When a certain file (mp4, flv, etc) has a 95 kbps audio bitrate - does it make sense outputing to a higher bitrate when converting to mp3 or other format (be it lossy or not)?
Would this result in higher audio quality or just in a bigger file?
Edits after a lot of answers+comments:
I am not talking about the output having better quality than the input: obviously, that is not possible. (Except for going from a lossless format to the original wave.) I am talking whether an output with a higher bitrate than the input will have a better quality than it might otherwise have.
please consider that I am aware that converting between lossy formats is not recommendable. Only that in some cases an original cd/wave may be unavailable. The question is just about the usefulness of optionally increasing the bitrate when converting.
maybe a sub-question is useful: is the answer dependent on the type of the output file (lossless or lossy)?
the most voted two answers below (this and this) seem to say different things, namely, the later says that Bitrates are not directly comparable and if the original audio is in a more efficient format, then the output (less efficient) audio should have a somewhat superior bitrate (the same idea here and here) - but while the less efficient is mp3, I am not sure which exactly are the more efficient formats. (is it aac?) (-- And in general the answers seem to fall in one of the two positions represented by the most voted answers.)
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If you are really curious as to why this doesn't help, read about Sampling Theorem. http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
– kmort – 2013-05-10T11:57:50.310I could imagine an algorithm that can upsample, and then smooth out the sound. I don't know if this is at all possible in practice – Andrey – 2013-05-10T14:15:22.997
8@kmort The Nyquist theorem has absolutely nothing to do with that. I dare say most MP3 files are sampled at 44.1 kHz anyway. The real issue is whatever lossy scheme is applied at the encoding stage (psychoacoustic filters etc.) – slhck – 2013-05-10T14:25:03.783
11I don't think he expects it to be of higher quality than the input source, but wants to know if, say, transcoding a 128kbs AAC to a 192kbs or 256kbs MP3 will sound better than if he transcodes it to a 128kbs MP3. I've wondered the same thing since I have a bunch of AAC files that I sometimes convert to MP3 since the car player only understands MP3. – Johnny – 2013-05-10T18:15:55.707
2@Johnny - exactly: I use Format Factory which allows changing the bitrate, so I wandered what was to be done – None – 2013-05-10T18:24:07.347
3Right; it's not a question of improving quality, but of minimizing the damage from doing another format shift. In that respect, yes, a higher bitrate target format makes perfect sense. Lots of kneejerk answers to this question. – Ask About Monica – 2013-05-10T18:31:06.153
2@kbelder You can't accuse people of providing kneejerk answers when the question was a little vague on that part to begin with. Of course, now that it's clarified, one could improve the existing answers. – slhck – 2013-05-10T19:08:14.140
1All these answers revolves around a very simple truth. Encoding an audio file (or video file) isn't much different from doing a xerox copy. In the best case, you will get a copy that is perceptually identical to the original. In worse cases, you will get a quality reduction.
Unlike xerox though, there are a category of codecs that are called lossless, because they preserve an identical copy of their input. Think of them as zip files. Zipping a Word document does not make letters disappear. Same goes for encoding sound to e.g. FLAC. – Niels B. – 2013-05-10T20:47:33.180
@NielsB. - all these basics are well known to me -- but please see latest edits. there is also another position here represented by the second most voted answer and also others like here and here
– None – 2013-05-10T20:50:20.9102@capricus, yes. The second answer is about the compression efficiency of the various formats. MP3 performs poorly compared to modern formats like HE-AAC. Basically, if you have a song encoded in HE-AAC, it might have a bitrate of 64 kbps (about 1 megabyte for normal song) and still sound acceptable. If you want to encode this file to MP3, you will suffer a massacre in sound quality, if you insist that your MP3 encoder must only consume 64 kbits of data pr. second of audio. – Niels B. – 2013-05-10T20:57:10.487
2They're both correct. By upping the bitrate, at best you get bigger files of the same quality. "Higher audio quality" can be interpreted as "higher than the original" or "higher than the resulting file encoded at the same bitrate". Higher than the original will not happen. Higher than the same thing done at a lower bitrate is true. I frequently try various rates and keep the smallest one that is acceptable to me. – LilCodger – 2013-05-10T20:58:58.750
In the same way, you might have a razorsharp business card printed at your local print house that has a delicate sharp font. If you throw this card into your scanner and try to print a copy on your cheap inkjet printer, you will get a blurry result. So to keep the text readable, you have no choice but to increase the size of the print to compensate for the lack of sharpness in the printer. – Niels B. – 2013-05-10T20:59:05.573
sorry for late coming.the answer to me is obvious that 1.Yes, it does. 2.Yes, better and bigger. To calculate the new bitrate needed is like decompressing and compress again and if your new format is Lossy then it does not ensure to give the same quality as in your old format no matter how high the bitrate you give.A trival example for concept. old algo is cutting the last x-hz of frequency ; and the new algo by cutting first x-hz of the frequency. for 123456789: => 1234567 and decompress to 123456700, then => 3456700, for better sampling in new algo: 23456700. sorry comment-length restricted. – Abby Chau Yu Hoi – 2013-05-11T19:25:58.033
would you take a look at this question (http://superuser.com/q/595777/162573)?
– None – 2013-05-15T10:00:21.077