sqlite timecode calculations - sqlite

Question

I have two tables which I export from my video editing suite, one ("MediaPool") containing a row for each media file imported into the project, another ("Montage") for the portions of that file used in a specific edit. The fields that are associated between the two are MediaPool.FileName and Montage.Name, which are very similar (Filename only adds the file extension).
# MediaPool
Filename | Take
---------------------------------
somefile.mp4 | Getty
file2.mov | Associated Press
file3.mov | Associated Press
and
# Montage
Name | RecordIn | RecordOut
------------------------------------------
somefile | 01:01:01:01 | 01:01:20:19
somefile | 01:05:15:23 | 01:05:16:10
somefile | 01:25:19:10 | 01:30:16:04
file2 | 01:30:11:10 | 01:31:18:12
file2 | 01:40:15:22 | 01:42:21:17
The tables contain many more columns of course, but only the above is relevant.
Only the "MediaPool" table contains the field called "Take" which designates the file's copyright holder (long story). It can't be included in the "Montage" export. I needed to calculate the total duration of footage used from each source, by subtracting the RecordIn timecode from RecordOut and adding each result. This turned out to be more complicated than I expected, as I have some notions of programming but almost none when it comes to SQL (sqlite in my case).
I managed to come up with the following, which works fine and runs in under 4 seconds. However, from the little programming I've done, it seems overlong and very inelegant. Is there a shorter way to achieve this?
BTW, I'm using 25 fps timecode and I can't use LPAD in sqlite.
SELECT
Source,
SUBSTR('00' || CAST(DurationFrames/(60*60*25) AS TEXT), -2, 2) || ':' ||
SUBSTR('00' || CAST(DurationFrames%(60*60*25)/(60*25) AS TEXT), -2, 2) || ':' ||
SUBSTR('00' || CAST(DurationFrames%(60*60*25)%(60*25)/25 AS TEXT), -2, 2) || ':' ||
SUBSTR('00' || CAST(DurationFrames%(60*60*25)%(60*25)%25 AS TEXT), -2, 2)
AS DurationTC
FROM
(
SELECT
MediaPool.Take AS Source,
Montage.RecordIn,
Montage.RecordOut,
SUM(CAST(SUBSTR(Montage.RecordOut, 1, 2) AS INT)*3600*25 +
CAST(SUBSTR(Montage.RecordOut, 4, 2) AS INT)*60*25 +
CAST(SUBSTR(Montage.RecordOut, 7, 2) AS INT)*25 +
CAST(SUBSTR(Montage.RecordOut, 10, 2) AS INT) -
CAST(SUBSTR(Montage.RecordIn, 1, 2) AS INT)*3600*25 -
CAST(SUBSTR(Montage.RecordIn, 4, 2) AS INT)*60*25 -
CAST(SUBSTR(Montage.RecordIn, 7, 2) AS INT)*25 -
CAST(SUBSTR(Montage.RecordIn, 10, 2) AS INT))
AS DurationFrames
FROM
MediaPool
JOIN
Montage ON MediaPool.FileName LIKE '%' || Montage.Name || '%'
GROUP BY
Take
ORDER BY
Take
)

Answer 1

Here's a simplified query that produces the same results as yours on your test data. Mostly it uses printf() instead of a bunch of string concatenation and substr()s, and uses strftime() to calculate the total seconds of the hours minutes seconds part of the timecode:
WITH frames AS
(SELECT Take, sum((strftime('%s', substr(RecordOut,1,8))*25 + substr(RecordOut,10))
- (strftime('%s', substr(RecordIn,1,8))*25 + substr(RecordIn,10)))
AS DurationFrames
FROM MediaPool
JOIN Montage ON MediaPool.Filename LIKE Montage.Name || '.%'
GROUP BY Take)
SELECT Take AS Source
, printf("%02d:%02d:%02d:%02d", DurationFrames/(60*60*25),
DurationFrames%(60*60*25)/(60*25),
DurationFrames%(60*60*25)%(60*25)/25,
DurationFrames%(60*60*25)%(60*25)%25)
AS DurationTC
FROM frames
ORDER BY Take;