Curious about some extra info about audio after replacing audio track

[OrangeCat]

I saved an audio track from one .mp4 video and replaced another track in a different video with it (both are the same exact movie with the same duration, same video/audio codecs, except one was 720p and the other was 1080p. I wanted to replace the 6ch sound in the 1080p with the 2ch sound from the 720p.)

After I finished, I noticed the mediainfo tab on my player says under the audio section that the "Source_Duration_LastFrame" is "-11ms". There is also something at the end about a "hdmd duration" with a line of numbers.

I did not notice anything odd when I watched the video. But I am curious as to what that info means.

(I am using nightly build from June 20th)

[eumagga0x2a]

I noticed the mediainfo tab on my player says under the audio section that the "Source_Duration_LastFrame" is "-11ms".

This is verbatim a part of MediaInfo output which means that the duration of the last audio frame is 11 milliseconds shorter than the duration of other audio frames, probably because the muxer which created the MP4 file trimmed the duration (not the frame itself, just the metadata) to match the total duration of the video track.

There is also something at the end about a "hdmd duration" with a line of numbers.

"mdhd" (media header atom in a QuickTime or MP4 file) contains a field "duration" to hold (if I am not mistaken the original = not influenced by edit lists) duration of the particular medium in the track in units of the medium's time scale, which in case of audio is usually the sampling frequency.

(I am using nightly build from June 20th)

There might be some more recent builds.

[OrangeCat]

Hello. Thanks for the reply.

So it is basically a "statistics" thing and not something that affects the actual video/audio?

Yes, I see there is two more versions after this. I just listed the version I was using in case it mattered for technical reasons. It was the latest version I downloaded at the time when I upgraded after the stable version from December.

[eumagga0x2a]

Both may matter. All depends on the player which interprets the structures of the container.