Re: [Qtractor-devel] Qtractor: imported mp3 / internal tempo go out of sync when moving the playhead

[Rui N. C. <rn...@rn...>]

On 2/19/19 1:10 AM, Nikita P wrote:
> 
> Just curious: is it a problem fixable with some effort or is it an
> inherent problem of mp3 compression, and making a workaround for that
> would be a pain in the ass?
> 

none that is worthy and yes there's a workaround already in place but
obviously it is not satisfactory not even close.

cheers
-- 
rncbc aka. Rui Nuno Capela
rn...@rn...


> On 19/02/2019, Rui Nuno Capela <rn...@rn...> wrote:
>> On 2/18/19 4:33 PM, Nikita P wrote:
>>> Qtractor version: 0.9.3.25git.337cf1
>>>
>>> Repro steps starting from an empty project:
>>> * add an audio track
>>> * import an mp3 file that has rhythmic content and place it into the
>>> track
>>> * set project BPM and tempo to the same amount as the mp3
>>> * (optional) fine-tune the audio clip position to synchronize the beats
>>> * turn on the metronome
>>>
>>> If I click play when the playhead is at the beginning of the project,
>>> metronome and the audio clip will be in sync. They will continue being
>>> in sync until the end.
>>>
>>> If I move the playhead further along the timeline and then click play,
>>> metronome clicks and the mp3's beats will be out of sync.
>>>
>>> I use the audio metronome, not the midi one.
>>>
>>> Here's a 120 bpm click track I created in Audacity you can use for
>>> testing:
>>> https://www.dropbox.com/s/skcc6mhjp5aeb9q/test_click_track.mp3?dl=0
>>>
>>> It seems to be an issue with playing back mp3 audio files. The same
>>> click track exported from Audacity as a WAV and then imported into
>>> Qtractor works fine. Tried ogg, and it was also fine.
>>>
>>> Additionally, when playing with the playhead at the start, the
>>> uncompressed/ogg click track is more in sync with Qtractor's metronome
>>> than the mp3 one.
>>>
>>
>> mp3 is not sample accurate, at least on the (more than a) decade old
>> implementation via libmad0...
>>
>> that said, stop or refrain to use mp3 audio files as time-sync
>> references in qtractor: you'll be doomed to fail badly as it gets quite
>>  a nuisance as farther you get in the timeline... you've been warned :)
>>
>> mp3 support ought to be removed from qtractor builds by default a long
>> time ago: don't rely on that sh*t ever--at least for synchronization
>> purposes: it will drift apart and you cannot recover from it. sorry
>>