Re: [FFmpeg-user] '-t' versus '-to'

[Bouke / edit 'B]

> On 14 Jan 2024, at 21:22, Carl Zwanzig  wrote:
> 
> On 1/13/2024 10:26 PM, Mark Filipak wrote:
>> For example:
>> -ss 20.061708 -to 5570.815250
>> would be
>> -frametrim 481..134046
>> meaning frame 481 thru frame 134046.
> 
> Although IME it much more common to specify the frame number after a dot* but 
> ffmpeg doesn't seem to do that. (There may be North American vs Europe vs 
> Asiatic regional conventions on this.)
> 
> *hh:mm:ss.ff, or occasionally hh:mm:ss:ff, but the latter is ambiguous if 
> either hh or ff are omitted
> 
> Perhaps some day I'll look at the command arg time parser to see what 
> assumptions are made and where they're documented.

Don’t feed the trolls.

Bouke


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Re: [FFmpeg-user] '-t' versus '-to'

[Carl Zwanzig]

On 1/13/2024 10:26 PM, Mark Filipak wrote:

For example:
-ss 20.061708 -to 5570.815250
would be
-frametrim 481..134046
meaning frame 481 thru frame 134046.


Although IME it much more common to specify the frame number after a dot* 
but ffmpeg doesn't seem to do that. (There may be North American vs Europe 
vs Asiatic regional conventions on this.)


*hh:mm:ss.ff, or occasionally hh:mm:ss:ff, but the latter is ambiguous if 
either hh or ff are omitted


Perhaps some day I'll look at the command arg time parser to see what 
assumptions are made and where they're documented.


z!
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Re: [FFmpeg-user] '-t' versus '-to'

[Mark Filipak]

PS: Actually, I think '-framespan' would be a better name for such a function.
-framespan 481..134046

On 13/01/2024 22.57, Carl Zwanzig wrote:

On 1/13/2024 7:37 PM, DEF wrote:

...other times you want to trim,..

...(I prefer frame numbers, myself.)


I wholeheartedly agree with you, Carl. For example:
-ss 20.061708 -to 5570.815250
would be
-frametrim 481..134046
meaning frame 481 thru frame 134046.
Since it specifies the starting and ending frames, time is not an issue and 
duration is explicit.
Trimming the audio, subtitles, and chapter list would be automatic and based on 
those frames.

--Mark.

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Re: [FFmpeg-user] '-t' versus '-to'

[Mark Filipak]

On 13/01/2024 22.57, Carl Zwanzig wrote:

On 1/13/2024 7:37 PM, DEF wrote:

...other times you want to trim,..

...(I prefer frame numbers, myself.)


I wholeheartedly agree with you, Carl. For example:
-ss 20.061708 -to 5570.815250
would be
-frametrim 481..134046
meaning frame 481 thru frame 134046.
Since it specifies the starting and ending frames, time is not an issue and 
duration is explicit.
Trimming the audio, subtitles, and chapter list would be automatic and based on 
those frames.

--Mark.

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Re: [FFmpeg-user] '-t' versus '-to'

[Carl Zwanzig]

On 1/13/2024 7:37 PM, DEF wrote:

other times you want to trim, you know your start time and end time
but perhaps you are lazy to calculate the duration.


Or don't see a need because you know the points :), AFAICT most human 
editors work that way.



the you use -to to denote your_position_  in the video  as in

-ss 00:12:03 -to 15:04:08 for example.


Brings another question- if you want to select 15 seconds and no additional 
frames starting at 00:00:03.0 do you give the out point as 00:00:18.0 or 
:17.999 or :17.29 (for a frame count, not a fraction of a second)? I suspect 
.999 will do the job, but it's cumbersome and not as simple to calculate. (I 
prefer frame numbers, myself.)


Later,

z!
in the land of 29.97
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Re: [FFmpeg-user] '-t' versus '-to'

[DEF]

On Sat, 13 Jan 2024 at 22:34, Jim DeLaHunt  wrote:
>
> Mark:
>
> On 2024-01-13 12:50, Mark Filipak wrote:
> > What's the difference?
> >
> > -t duration (input/output)
> > When used as an input option (before -i), limit the duration of
> > data read from the input file.
> > When used as an output option (before an output url),
> > stop writing the output after its duration reaches duration.
> > duration must be a time duration specification, see
> > (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1)
> > manual.
> > -to and -t are mutually exclusive and -t has priority.
> >
> > -to position (input/output)
> > Stop writing the output or reading the input at position.
> > position must be a time duration specification, see
> > (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1)
> > manual.
> > -to and -t are mutually exclusive and -t has priority.
> To be clear, I believe that the above two paragraphs are direct quotes
> from the FFMpeg documentation, 5.4 Main options
> .
> > 'duration' and 'position' seem to both be duration. What's the
> > difference?
>
> That is a great question. The FFMpeg documentation should be clear about
> the meanings of these parameters, and the difference between the
> meanings of the terms "duration" and "position". It is not.

I think the documentation is clear there.

Many at times one knows the duration for which they  intend to trim.
if that be the case and you are starting from 0, then -t is used. and
the _duration_ of the output video specified.

other times you want to trim, you know your start time and end time
but perhaps you are lazy to calculate the duration.
the you use -to to denote your _position_ in the video  as in

-ss 00:12:03 -to 15:04:08 for example.

DEF


>
> I do not see these terms defined outside of section 5.4. I see 95
> occurrences of the word 'position' in
> . I count at least four meanings for
> this term: a moment in the timeline of a media file's events; the x,y
> coordinates of a pixel (more rigorously, the cartesian coordinates of a
> point in the two-dimensional display space); the byte offset of a piece
> of data in the data stream; and the index within a character string of a
> data field.  There are several parameters of various options and
> filters, documented by the word "position", with no explanation of the
> meaning FFMpeg assigns to the word.
>
>  > …'duration' and 'position' seem to both be duration.…
>
> You use the word 'be'. Now technical writing is difficult, and I am not
> an expert at it. But my non-expert opinion is that the English verb 'to
> be' is often a poor choice for use in technical statements. The English
> language makes 'to be' carry a wide range of meanings, so statements
> using 'to be' might be unclear.
>
> I would say, 'duration' and 'position' both take parameters having a
> syntactical format of 'time duration' as specified in the
> ffmpeg-utils(1) manual.
>
> I am also not an FFmpeg expert. The true answer to your question
> probably lies in reading the code. And the code itself may have
> multiple, conflicting answers. But I will guess that 'duration' refers
> to a portion of a media file timeline, and 'position' refers to a moment
> in the media file timeline. They are perhaps analogous to 'line segment'
> and 'point' in geometry. 'position' is perhaps that moment in the
> timeline which occurs at the given timespan after the beginning of the
> timeline, though it could be the moment which has the given time value
> relative to time zero in the timeline.
>
> Those are just my non-expert guesses. I will be interested to hear the
> correct answer(s). And I wish we could look up those answer(s) in the
> FFMpeg documentation.
>
> Good question!
>   —Jim DeLaHunt
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Re: [FFmpeg-user] '-t' versus '-to'

[Jim DeLaHunt]

Mark:

On 2024-01-13 12:50, Mark Filipak wrote:

What's the difference?

-t duration (input/output)
    When used as an input option (before -i), limit the duration of 
data read from the input file.

    When used as an output option (before an output url),
    stop writing the output after its duration reaches duration.
    duration must be a time duration specification, see
    (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) 
manual.

    -to and -t are mutually exclusive and -t has priority.

-to position (input/output)
    Stop writing the output or reading the input at position.
    position must be a time duration specification, see
    (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) 
manual.

    -to and -t are mutually exclusive and -t has priority.
To be clear, I believe that the above two paragraphs are direct quotes 
from the FFMpeg documentation, 5.4 Main options 
.
'duration' and 'position' seem to both be duration. What's the 
difference?


That is a great question. The FFMpeg documentation should be clear about 
the meanings of these parameters, and the difference between the 
meanings of the terms "duration" and "position". It is not.


I do not see these terms defined outside of section 5.4. I see 95 
occurrences of the word 'position' in 
. I count at least four meanings for 
this term: a moment in the timeline of a media file's events; the x,y 
coordinates of a pixel (more rigorously, the cartesian coordinates of a 
point in the two-dimensional display space); the byte offset of a piece 
of data in the data stream; and the index within a character string of a 
data field.  There are several parameters of various options and 
filters, documented by the word "position", with no explanation of the 
meaning FFMpeg assigns to the word.


> …'duration' and 'position' seem to both be duration.…

You use the word 'be'. Now technical writing is difficult, and I am not 
an expert at it. But my non-expert opinion is that the English verb 'to 
be' is often a poor choice for use in technical statements. The English 
language makes 'to be' carry a wide range of meanings, so statements 
using 'to be' might be unclear.


I would say, 'duration' and 'position' both take parameters having a 
syntactical format of 'time duration' as specified in the 
ffmpeg-utils(1) manual.


I am also not an FFmpeg expert. The true answer to your question 
probably lies in reading the code. And the code itself may have 
multiple, conflicting answers. But I will guess that 'duration' refers 
to a portion of a media file timeline, and 'position' refers to a moment 
in the media file timeline. They are perhaps analogous to 'line segment' 
and 'point' in geometry. 'position' is perhaps that moment in the 
timeline which occurs at the given timespan after the beginning of the 
timeline, though it could be the moment which has the given time value 
relative to time zero in the timeline.


Those are just my non-expert guesses. I will be interested to hear the 
correct answer(s). And I wish we could look up those answer(s) in the 
FFMpeg documentation.


Good question!
 —Jim DeLaHunt
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[FFmpeg-user] '-t' versus '-to'

[Mark Filipak]

What's the difference?

-t duration (input/output)
When used as an input option (before -i), limit the duration of data read 
from the input file.
When used as an output option (before an output url),
stop writing the output after its duration reaches duration.
duration must be a time duration specification, see
(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.
-to and -t are mutually exclusive and -t has priority.

-to position (input/output)
Stop writing the output or reading the input at position.
position must be a time duration specification, see
(ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.
-to and -t are mutually exclusive and -t has priority.

'duration' and 'position' seem to both be duration. What's the difference?

--Mark.
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