Hi Paul,
I have had to deal with differing player intervals or timeScales in my
application which I develop on the Mac working with the player in LC. It uses
Video files only. I first realized this was a problem when I would create a
project file that annotates a video then later compress the video and the next
time I would open the project file all the time based data was off even though
it was the same video. I found that the compression program used a different
timeScale than the original movie depending on the compression codec, frame
rate etc.
What I had to do to deal with the varying timeScales was do a conversion to a
common timescale that I used in the application and when saving to the project
file. I used an application/document timescale of 1000/second. I had
considered a number of options i.e. something divisible by 30 for 30 FPS, using
another common timeScale like 600 or 90000.. In the end I used 1000 or
1000/second since milliseconds is property I used in the application for
tracking user action so I considered that a time scale that was native to the
application.
When I retrieved any of the Player’s time properties - currentTime, startTime,
endTime, timeScale, and duration etc. I would convert them with the following
function to the 1000/sec common timeScale
function convertPlayerTimeScaleTo1000 pTime, pTimeScale
if pTimeScale = 0 or pTimeScale is empty then
# This is to prevent Divide by zero errors or other issues if
timeScale is empty
put 600 into pTimeScale
end if
local t1000Scale
put round(pTime/pTimeScale * 1000) into t1000Scale
return t1000Scale
end convertPlayerTimeScaleTo1000
Then when I set any of those properties I use this function to convert back
from the application timescale 1000/sec to the native timeScale.
function convert1000ToPlayerTimescale pTime, pTimeScale
local tNativeScale
put round(pTime/1000 * pTimeScale) into tNativeScale
return tNativeScale
end convert1000ToPlayerTimescale
I did not notice big differences in values when I used different codecs from
the same video but I guess that makes sense since I am only working on the Mac.
My application will be running on Windows as well so that is something I am
going to have to test.
Regards,
Martin Koob
> On Feb 18, 2020, at 10:13 AM, Paul Dupuis via use-livecode
> <use-livecode@lists.runrev.com <mailto:use-livecode@lists.runrev.com>> wrote:
>
> Or even more specifically, does any one know what player object "intervals"
> (the values for currentTime, startTime, endTime, timeScale, and duration
> properties of a player) actually are? Are they frames? Something else? And
> does anyone know why they vary by Media Framework (i.e Quicktime vs Apple
> Video Foundation vs DirectShow)
>
> For example, the same MP3 file under Quicktime (macOS or Windows) has a
> timeScale of 600, and under AVF a timeScale of 44100 and under DirectShow a
> timeScale of 10000000.
>
> What's more if you get the duration and the timeScale and convert to seconds,
> the different frameworks give (slightly) different values (largest difference
> is 3s on a 2m45s MP3)
>
> For example, look at the lengthy list of data below: This is timeScale and
> duration for different file formats by media frameworks. A file of the same
> name (i.e. audio.aac) is the SAME file on any media Framework that can read
> it. Formats readable by the player differ by Media Framework. The data is tab
> delimited, so if the listserv preserves the tabs, you should be able to cut
> and paste to a spreadsheet for easier viewing.
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