On 2021-03-04 09:26, Moritz Barsnick wrote:
On Thu, Mar 04, 2021 at 03:57:38 -0500, Mark Filipak (ffmpeg) wrote:
Well, per rational.h, 'num' & 'den' are both integers.
Now, I don't know how '720000' is stored. Is it stored as an int64?
They are defined as "int", which can be platform dependant. ffmpeg
assumes/guarantees ints to be at least 32 bits.
I don't know, but I do know that it can't be stored as an 8-bit
integer or a 16-bit integer or anything else that has 8-bit or 16-bit
resolution.
If you mean the number 720000, that's correct.
That includes AVRational. 720000 can't be stored as
AVRational. AVRational just doesn't have enough resolution.
Huh? You didn't even wait for the answer to how it is stored. And you
even asked whether it was 64 bits. This would work just fine with 64
bits.
It's a rational number of two integers with at least 32 bits...
Ah! An 'int' is a signed, 32-bit integer (aka int32_t). Okay. Good to know.
Thanks.
... 1/720000
is probably stored as { 1, 720000 }, but could also be { 2, 1400000 }
for example, unless they get reduced automatically (I'm too lazy to
check).
So, TB is stored as an AVRational: 'num', 'den', each signed, 32-bit integers. Okay. Good to know.
Thanks.
No problem then. I think that just about clears everything up. You see, I'm not a 'C' programmer and
it appears that just what an int *is* varies. I guess that's why the 'C' world has standardized on
calling the datatype "int32_t", eh?
I'm sure you know that the running time produced by 'PTS's depends on frame
rate *and* time_base. For example, for 23.976fps and TB = 1/(720000 ticks/s)
= 1.3[8..] µs/tick, a PTS of +9223372036854775800 indicates a
307138595965860 maximum frame number.
Huh? At 720000 ticks/seconds, and PTS being number of ticks, you can
create timestamps spanning
(2^63 - 1) / 720000 seconds
which is
~12810238940076 seconds
which is
~400000 years.
Where am I going wrong?
A maximum frame number, N, of 307138595965860 frames at 24/1.001 frames/s yields a running time of
12810238940076.0775 seconds. So we're in agreement I think.
Oh! I see. I wrote this: "That frame number is reached by a 426581383 second video (= 13 years, 189
days, 49 minutes, 43 seconds)." I apparently divided maximum running time by deltaPTS (30030). Why
did I do that? Well, that was at 4AM. I was getting pretty punchy. Sorry.
Do you agree with my figures? Do you see the difference between time
extents and time resolution?
I don't agree with your figures.
I swear: That is the last mistake I will ever make (for all time). :-)
--
In U.S. History: The House Un-American Activities Committee was a committee of the House of
Representatives that engaged in un-American activities.
_______________________________________________
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user
To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
