Join Motion JPG (mjpeg/mjpg) without re-encoding

[giroro]

Because my camera automatically takes movies in Motion JPG format and it automatically splits the movie if a clip becomes larger than a certain size, I I have a lot of motion JPG movie clips that are parts of the same movie. I've been trying to merge/join them without re-encoding (because re-encoding will reduce the quality and my clips are not of high quality to begin with).

I tried several methods, but without much success. I tried Avidemux, but for some reason, it seems to re-encode the movies judging from the fact that the joined movie files are much larger than the sum of the size of the combined files (e.g., 100M + 100M = 400M). It is also very buggy, and tends to crash a lot, and it does not work for some movies.

Do you have any suggestion about how I can join multiple Motion JPG files (lossless)? I would really appreciate your help!

[pandy]

Perhaps? https://trac.ffmpeg.org/wiki/How%20to%20concatenate%20%28join,%20merge%29%20media%20files

[jagabo]

What container?

[giroro]

Hi Pandy, thank you for your suggestion. I found a few posts on FFMPEG, but haven't been able to figure out how to use it. I am not crazy about command-based software, but if this is the only option, I will give it a shot. Thanks!

Hi Jagabo, are you asking which container I want to pack the clips? If so, I don't have any specific preference when it comes with the container. Thanks.

[poisondeathray]

He's probably asking what container is it originally in

Because if it's AVI, then you could use vdub

If it's MOV, then you could use mpegstreamclip or quicktime pro

[giroro]

Whoops. Sorry for my misunderstanding. Most of my files are AVI, which probably means that the container is AVI (I have only rudimentary knowledge on this subject). So it appears that VDub is a good tool for AVI. But like FFMPEG, it is a command line program. Is there any program with a GUI? Avidemux is one, but it is too buggy to be practical. Thank you.

[pandy]

So it appears that VDub is a good tool for AVI. But like FFMPEG, it is a command line program. Is there any program with a GUI?

VirtualDub is a GUI program with Command Line capabilities if desired - over 99% VDub users use this superb software only in GUI mode.

[jagabo]

Yes, I was asking what container the source files were. VirtualDub is a good GUI program for working with AVI files. I'm surprised AviDemux was giving you problems with MJPEG in AVI though.

[giroro]

Thank you for enlightening me. I tried VirtualDub, and it worked well for several of my clips. I joined 3 sets of clips, and haven't encountered a problem yet. Thank you for your helpful suggestions!

@jagabo, for some unknown reason, AviDemux gives me either of the following two issues: (1) the resulting movie is much bigger in size than the sum of the joined files (although I selected "copy")--apparently, it re-encoded the clips; or (2) the resulting movie doesn't play or plays in a choppy manner (as if there is some issue with encoding). I tried about 4 different sets, and none was successful. Perhaps it is due to the idiosyncrasy with my clips.

Thank you all for your suggestions and help!

[giroro]

I was happy with the first 3 attempts, but I encountered an issue. When I tried with some clips, VD gave me an error message saying that it cannot join the clips due to different sampling rates. Upon inspection, I found that the sampling rates are slightly different (29.000013 vs. 29.000028, etc.). These are the clips that were automatically split by my camera (all shot at the same time continuously).

So I hit another wall. Any suggestion or tip? Thank you in advance.

[jagabo]

As you've discovered, VirtualDub won't append clips that have slightly different frame rates. You can use VirtualDub to change the frame rate so they all match exactly. Open a file, Select Video -> Direct Stream Copy, then Video -> Frame Rate. In the top part of the dialog select Change Frame Rate To FPS, and type in a value. Finally, File -> Save as AVI. Do that for all clips you intend to join.

There is also a program called AviFRate that lets you change the frame rate without remuxing the file. It just changes the frame rate values in the AVI header. You have to be careful with the program because there are three values you can set. AVI files contain two integer values from which the frame rate is derived, a numerator and a denominator. A "30 fps" video might have 30 as the numerator and 1 as the denominator, or 30000 as the numerator and 1000 as the denominator. (VirtualDub would treat those two videos as having different frame rates.) AviFRate lets you specify the numerator, the denominator or the resulting rate. But sometimes it calculates the other values when you enter one. And since it uses integer math for the numerator and denominator, and limited precision floating point for the rate, you may not get exactly the rate you want. Before saving make sure the numerator and denominator show the correct values.

Regarding too large files with AviDemux: I don't remember if AviDemux does this but some programs automatically append files with sequentially numbered names. VirtualDub, for example. Say you have three files named video1.avi, video2.avi, and video3.avi. In VirtualDub, File -> Open Video File will open only one file. But File -> Append AVI Segement will append the file you specify and any sequentially named files (there's an option to disable this on the Append File dialog). Say you open File1.avi. And then append video2.avi -- video3.avi will automatically be appended too. If you then manually append video3.avi, that segment will appear twice. AviDemux might do the same. That would explain why your resulting files were larger than expected.

AviDemux is more forgiving about the frame rate of appended AVI files.

[giroro]

Dear jagabo, thank you for your tips. I will definitely try the trick you suggested. I am a little concerned about this approach because the program warns me that changing framerates could destroy the sync between audio and video, but making a very small change (e.g., 29.00007 vs. 29.00012) won't really screw up the sync. I will give it a shot.

As far as Avidemux is concerned, I don't think the duplication is the cause of the large size. I tried another clip today. The original clip was about 2GB, and I chose "copy" for both video and audio, and selected "AVI demux" for the container (I didn't even try to append; just tried to copy the clip basically). However, the resulting clip was over 4GB. No duplication, and the clip played well. Am I missing something here?

Many, many thanks!

[jagabo]

As far as Avidemux is concerned, I don't think the duplication is the cause of the large size. I tried another clip today. The original clip was about 2GB, and I chose "copy" for both video and audio, and selected "AVI demux" for the container (I didn't even try to append; just tried to copy the clip basically). However, the resulting clip was over 4GB. No duplication, and the clip played well. Am I missing something here?

Strange. It's supposed to work like that. With Video and Audio set to COPY it should just remux. There must be something it doesn't like about your files.

[giroro]

Strange. It's supposed to work like that. With Video and Audio set to COPY it should just remux. There must be something it doesn't like about your files.

It is indeed strange. I suppose that there is some sort of incompatibility as you noted.

Thank you for your advice. It has been extremely helpful.