why there is difference between duration of orignial video and dwnloaded

[jraju]

Hi,
i think that the duration of the video would not change, even if you convert to some other format, say mkv to mp4 format or avi format.
but i noted that there is "second" one second difference between the original mkv and converted mp4.
is it correct if so, what is the reason for the difference
i also noted that some videos have no difference.
please enlighten me on both the points

[jagabo]

The duration of a video reported by programs is often an estimate.

[jagabo]

And sometimes the length in the header is an estimate. When you download the video the muxer might determine the length more precisely. Sometimes the video and audio will have different lengths. The length in the header may indicate the video length or the audio length. Or the audio may start at a different time than the video. The length in the header may be whichever ends first or last or just the length of one of them. In other words, there are many many different possible reasons why the length may differ after a download or remux.

The real test is to play the two videos and see if the length differs.

[jraju]

Hi, jagabo,
do you mean to say , to open and see the play time and then compare with the original.
the length is shown in explorer, would that change , when playing.
what if the original is mkv and the muxed is mp4.
A movie runs the same time as in original, is it not.

[jraju]

Hi, i just noticed that not few seconds , but just one second duration in alll the videos downloaded from the original videos duration.
please now say, what would be the reason. i checked the duration of both original and downloaded.

[jagabo]

I already gave you a bunch of reasons the reported lengths may differ.

[abolibibelot]

The informations provided in (supposedly Windows) explorer are not reliable / accurate (sometimes for instance a modified date like 10:05:58 gets rounded up to the upper minute, so it displays 10:06, in the explorer, but for other file types / extensions that's not the case, why is a mystery, there are so many weird things like that in the computer world, and in the world for that matter, I haven't bothered to solve that one).
Normally VirtualDub2 (for instance) should report the exact same duration for both the original and converted video.