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Offset in mp3-playback


when i import mp3 files into an audio-track, playback seems to be ofsync. Playing back the track from its beginning seems to works. But if i move the position of the playhead to another location within the clip manually, it does not start to play from the correct point in time. This could be seen best, if you have two audio-tracks. Import the same file twice, first as a mp3 on the one track and second as a wave file on the other track. Make sure they are positioned at the same statingpoint. If you hit play and move the playhead around, the offset of those two file should be hearable. Seems like qtractor is decoding mp3s on the fly? By the way, it's really convinient to have such a broad support of audio formats.

greets, fuchs

rncbc's picture

that is all a well known short-coming to mp3 format: mp3's doesn't allow or cope with frame accurate seek or relocation: you often have to decode the nearest header and block all the way to the point or frame you seek for: and if the mp3 is encoded as VBR (variable-bit-rate) than forget all hope of accuracy or precision on that matter.

bottom line is, kind of a caveat emptor: don't count on frame accuracy when dealing with mp3 files--it's a PITA--and mp3 support in qtractor (via libmad) has been just as naive as convenient it goes.

and now i even remember, i've been considering dropping it altogether, as i don't have use for no mp3's, for years now. as the old flick says: quite frankly my dear, i don't give a damn (to mp3 anymore) ;)

sorry but true

I expected somthing like this(as i stumbled upon the same seek issue on a small project i was working on).. i think in case of the current implementation, dropping would be a good thing to do as it is unusable. It just brings new users trouble, especially if they are not being super professinal, having all footage in raw lossles formats. Maybe it would be possible to refactor the support of other formats in a way that it just decodes them during import and saves them in the internal format? That would not completly give up the convinience or support for other formats. Sorry for bothering you with things that are unessential for you..

On a related note, qtr still uses ogg as the default file format, and that's baaaaad!

Please make wav, flac or basically anything lossless the default please Rui!

rncbc's picture

hi Dan

you can make it whatever you wish, it's an user preference setting (View/Options.../Audio/Capture & Export/File type)

i believe you know that well indeed ;)


I know that Rui but I'd just like to see qtr ship with more sensible defaults, thats all.

Not everyone knows what lossy formats are and why they shouldn't record using them hence my repeated suggestion.

rncbc's picture

and then, imho. ogg vorbis is a pretty one, all round, high-quality lossy format though.

its main advantage, for the sloppy newcomers at least (that i can think of) is about being innocuous to the nefarious hard-clipping distortion glitches you may get when signal goes overboard (ie. > 0dbfs); meaning that you may not hear it when monitoring but the recorded audio file gets severely crippled beyond any reasonable doubt. which is a bad and for all means lousy recording take anyhow.

and again, repeated "ad nauseum" before, qtractor is not meant to be a mastering tool--mastering as in the "Bob Katz sense", i say ;)

when producing something for real, and probably in a so-called professional scenario, fwiw. the most sensible default should be a lossless float 32-bit sample format. i, meself dixit!


So how about changing the default file type to 32-bit float WAV, AIFF or FLAC? Multi hundred MB files aren't a big deal when 2TB drives are common.

I'd rather qtr err on the side of audio quality rather than preserving disk space. If you think 32-bit float is overkill as a default then please make 16-bit wav the default instead. Surely that'd provide better sound than ogg for those who know how to record a non-clipping signal whilst obviously consuming a bit more disk space. I think its a better trade off as a default.

Just make the default lossless please and I'll quit this campaign of terror ;)

Hehe, changing the format to flac was exactly the first thing i did, when i was looking through the configuration at the very beginning :) But on the other hand, it made me recognize, that qtractor is able to also save things as ogg(but not shure if someone really wants to). I'm somewhat glad there is no option for choosing mp3 (would be very funny having all recordings being offsync ;)

rncbc's picture

ok. will make it generic "wav" as the factory default, starting in next couple of weeks, svn trunk ofc. ;)

by people demand, as they say;)


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