MKV to MP4, does vbr changes to cbr?

[socrates]

hey,

I have a movie in mp4 format. The contents are as follows, video- vbr- (bitrate 2500 to maximum bitrate 12.2 mbps) and variable frame rate 23.976 to 19.048 avc @ vbr and audio- aac @ vbr. I use TEncorder to change the file to mkv format, video- unchanged and audio- ac3 @ 384 cbr. When I use mediainfo, I get result as video details doesnot mention it as vbr but just 2500 and frame rate changed to constant frame rate @ 23.202. I have used setting not to alter video stream. Does change in container cause this?

Thanks

[Baldrick]

Try instead mkvtoolnix / mkvmergegui. In mkvmergegui (mmg) add your mp4 and then make a new mkv.

Or do you mean mkv to mp4(your thread title)?

[socrates]

Try instead mkvtoolnix / mkvmergegui. In mkvmergegui (mmg) add your mp4 and then make a new mkv.

Or do you mean mkv to mp4(your thread title)?

I think I got the title wrong. I have mp4 and I want to make convert it to mkv. But it seems that vbr of files in mp4 gets altered anyway though I choose direct stream copy. I hate when it gets altered. I want to preserve that vbr frame rate and bit rate. Does your suggestion help to preserve video file?

[Baldrick]

Yes. Mkvmergegui will preserve the video and audio. It will not reconvert but just change container. Try it!

[socrates]

Yes. Mkvmergegui will preserve the video and audio. It will not reconvert but just change container. Try it!

Just did what you have suggested. Mediainfo says variable bitrate has changedto cbr and variable frame rate to fixed....sad!

[Baldrick]

Do you get audio sync issues?

[socrates]

Do you get audio sync issues?

Nope....no audo sync issues.....

[sneaker]

Then there is no problem. Ignore what MediaInfo says. Mkvtoolnix does not re-encode in any way.

[Selur]

I agree, MediaInfo isn't that reliable when it comes to vbr vs cbr and vfr vs cfr.

[ValenNC]

Nor interlace detection, which seems to be really challenging to find a reliable app.

[socrates]

Hello again,

I'm trying out handbrake, latest 64 bit version. What is the setting to use to do video stream copy without any encoding? I can't seem to find any.

[Detmek]

You can not do that with Handbrake. If you want to change container type from MKV to MP4 use MP4Box. If you want to change container type from MP4 to MKV use MKVMerge (MKVToolnix).

[abolibibelot]

If the conversion takes a very short time (say, a few seconds, or less than 1 minute for a ~2h movie), then no actual transcoding was involved. Maybe the information for the original video was wrong (especially regarding the "variable frame rate", doesn't seem standard, others may elaborate on that), or maybe MediaInfo doesn't correctly detect those parameters on the converted MKV.

You can verify the bitrate profile using Bitrate Viewer : if both videos have exactly the same profile (and exact same average bitrate -- BV's analysis being much more accurate than MediaInfo's), then the streams are identical as they should be.

You can also go full-on OCD (as I would do in such a case) : demux audio & video streams for both files, then check their checksums (CRC32 or MD5, many tools for that), or open them in an Hex editor, like WinHex, which has a "synchronize and compare" function (and can calculate MD5, and also can compare two files and log their differences in "Tools" > "File tools" > "Compare"). To demux the streams, MPlayer works fine (TSMuxer GUI often works with MP4 but not always, MKVExtract as the name implies only extracts streams from MKVs, MPlayer works with everything that can be played), with such a command line (I assumed you're working on a Windows system ; change the drive letters, paths and names according to your configuration ; you may already have an mplayer.exe file somewhere inside a video converter installation folder, if so there's no need to download another) :

"X:\Path_to_MPlayer\mplayer.exe" "X:\Path_to_your_source_file\source_file.mp4" -dumpvideo -dumpfile "X:\Path_to_your_converted_file\source_file-videodemux.264"
"X:\Path_to_MPlayer\mplayer.exe" "X:\Path_to_your_source_file\source_file.mp4" -dumpaudio -dumpfile "X:\Path_to_your_converted_file\source_file-audiodemux.aac"
"X:\Path_to_MPlayer\mplayer.exe" "X:\Path_to_your_converted_file\converted_file.mkv" -dumpvideo -dumpfile "X:\Path_to_your_converted_file\converted_file-videodemux.264"
"X:\Path_to_MPlayer\mplayer.exe" "X:\Path_to_your_converted_file\converted_file.mkv" -dumpaudio -dumpfile "X:\Path_to_your_converted_file\converted_file-audiodemux.aac"

(Copy that into a text file, change the names/paths according to where each file actually is on your system, and where you want the demuxed stream files to be created, save, change extension from .txt to .bat, double-clic on that .bat file, wait a few seconds/minutes depending on the size of those files, then you should have video and audio streams for both files in the same folder as your converted MKV, now you can play with them until your mind is at peace.)

[socrates]

Thanks abolibibelot,

The suggestion looks very complicated atleast on paper. I shall try with the easy step, that is download the suggested bit rate viewer and try again.