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-   -   Tempo doubling on playback (http://www.notation.com/vb-forum/showthread.php?t=3707)

Tim Mariott 05-20-2011 05:11 PM

Tempo doubling on playback
 
I use a laptop running Vista to playback music for our choir practices. On some occasions, it is happily playing a piece when suddenly the tempo doubles. There is no change of tempo indicated in the score and if you look at the graph over notes this shows a steady tempo.
Sometimes closing the file and reopening it will fix the problem: sometimes restarting Notation: sometimes restarting the laptop: other times I just have to re-assign the correct tempo to the measures that we are rehearsing.
All of this of course takes a considerable amount of time and is very inconvenient and embarrassing for the rehearsal leader.
I have not yet been able to establish a pattern and before I do a lot of research I am wondering if anyone else has reported a similar problem: I cannot see anything on the forums but it is a tricky topic to search.
Can you give me any advice? For example, am I wasting time closing and reopening the file as the problem is more likely to be in the software than in the file?
Thanks
Tim

Sherry C 05-21-2011 12:59 AM

Re: Tempo doubling on playback
 
Hi Tim,

We haven't had any other reports about such a problem. Is it consistently the same file(s)? Does the behavior repeat itself specifically for the file if you stop, "rewind" to the front, and play it again without doing anything else besides that?

If you've got a particular file that is showing the behavior, you can send it to me at the Helpdesk (support@notation.com) and I'll take a look at it.

Thanks,
Sherry

Tim Mariott 05-23-2011 01:50 PM

Re: Tempo doubling on playback
 
Sherry
I have now found that the problem does occur consistently in a specific file on both my laptop running Vista and my desktop running Windows 7 Professional (64 bit).
The attached file is an arrangement of a selection of Rogers and Hammerstein tunes.
1. If you start the playback from measure 228, this should be "It might as well be spring" playing at a constant tempo of 75.
2. But when you get to measure 254, the playback suddenly speeds up, though the tempo display and Graph over Notes does not show any change.
3. However when you reach measure 267 there is a tempo change to 120 for the next song.
I cannot be precise about the speed up at measure 254, but it could well be to a tempo of 120.
So my instinct tells me that perhaps the software has read a whole chunk into memory, noted the tempo change but has applied it pre-emptively some 23 measures before it should be applied. Of course without knowing your software I may be completely wrong but that makes more sense to me than a completely random change of tempo.
I have had other songs where this has happened but I have not made a careful note of the details. If this example is not sufficient I will look out for another.
Thanks
Tim

Sherry C 05-23-2011 03:52 PM

Re: Tempo doubling on playback
 
Hi Tim,

Thanks for the file - I am definitely able to hear the problem.

The general case seems to be as you surmised - the tempo changes (both slower and faster) in some cases are applied too far ahead. The caveat that I'm seeing is that it occurs only after some length of measures (which I haven't ferreted out yet). There is a tempo change at measure 32 which does not cause earlier measures to suddenly change tempo, but later on in the file tempo changes are implemented ahead of the graph/event of the tempo change. For example, there is a tempo change at measure 225. If you play back the file starting around measure 210, then that tempo change actually kicks in at measure 214 rather than at measure 225 where it's supposed to. The same problem occurs as you mentioned in your post.

The problem has probably been around for a while, but since very few users create such long files, it has just not shown up. I haven't been able to come up with a good work around for you at present, other than to manually go in, ferret out where the incorrect tempo changes are occurring, and adjust accordingly to fit the music better. It's a totally unacceptable (from a programming point of view) workaround, but at present I have no better one to offer. I'll write this problem up for fixing, but we're in transition right now (looking for a developer since the passing of Mark Walsen) so I can't make any promises about when the problem will get fixed.

Sorry for the bother here. This sounds like a great choral medley to perform - I wish I were singing with you folks!

ttfn,
Sherry

task 2426

BarrieB 05-23-2011 04:45 PM

Re: Tempo doubling on playback
 
Hello Sherry/Tim,

I have downloaded Tim's file and can confirm the behaviour which he describes, and also note that the file plays back correctly when played from the beginning.

I can also say that I have encountered a similar behaviour myself quite recently. Its my belief that this has something to do with repeated sections. I was working on a file which contains repeated sections ( as does rogers.not), and when editing the tempo map, to try and put in rall's and fermatas, I was finding that when commencing playback from mid song,to test the tempo changes, the tempo changes were not happening where the graph said that they should be, but everything played correctly when commencing playback from the start of the song. I will try to locate where this was happening and perhaps attach a file tomorrow, if I can reproduce the symptoms.

It was like when starting playback from mid song, the bar count in the tempo map, did not match the bar number of the current measure playing back.

Hope that this helps

Regards,

Sherry C 05-23-2011 05:04 PM

Re: Tempo doubling on playback
 
Hi Barrie (and Tim),

Thanks for the additional insight here! That points the way to a workaround that hopefully will work for a rehearsal file, if not for the "pretty print" version.

Tim, I just tested this and it works. Hopefully it will be a workaround that you can use for practices anyway, although it does lose your Rehearsal marks (ouch - sorry). Open your file and use File/Export as MIDI, and be sure to check the "Write out repeats" option, then you'll get a full-length rehearsal file that will play the proper tempos (yeah, it should be "tempi", but that sounds funny ;) ) at the proper places, even if you stop and restart playback midway through the file.

Thanks for the added insight Barrie - I'm adding this to the "fix it" notes.

ttfn,
Sherry

Tim Mariott 05-23-2011 05:17 PM

Re: Tempo doubling on playback
 
Sherry/Barrie
Synchronised solutions! I had just carried out the same test by doing a MIDI export. This does give me an adequate workaround provided I remember to use the MIDI file rather than the Notation file in the white heat of our rehearsals. I will have to make a note of which of my current pieces have repeat marks and tempo changes - or perhaps best to set up a "rehearsals folder" with all MIDI versions. And hopefully this gives a clue for an eventual fix.
I am sorry to read the news about Mark Walsen: clearly a guy with a love of performing music.
Best wishes
Tim


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