Convert MP4 back to avi

[Duschkoenig]

Hi!

Some while back I encoded a lot of DivXs using DivX 5.0.2 and MP3 audio. I then converted the avis to mp4 using the converter in DivX 5.0.2 (Don't ask why, I would still be ashamed!). The only application being able to play those files is The Player which I did not mind at the time.

However, I would need the files as avi now and no apllication seems to be able to read the mp4s. Can anybody help me how convert those files back to avi?

DK

[bond_d9]

there a lot of applications available already which handle .mp4 files (.mp4 is the container format defined in the mpeg-4 standard)

for playback of .mp4 files the best would probably to install 3ivx, which lets you play .mp4 files in all dshow based player (ie wmp), also together with the ffdshow, xvid or divx5 decoder filter if you prefer that

if you want to convert from .mp4 to .avi you can also use mp4ui

[Duschkoenig]

Thanks a lot. I have also done some reasearch. The problem seems to be that the DivX 5.0.2 converter was not fully .mp4 compliant. Seems they removed it from 5.0.3 onwards because of that reason.

I have already tried 3ivx. And it enables the playback in Windows Media Player 9 which was not possible before installing 3ivx.

I also tried to extract the streams with with the mp4tools found on http://www.rarewares.org/mp4.html . That worked fine for the audio track. It playes fine as an mp3. However the video track does not play at all. Neither as a .mp4 nor as a .avi. I believe the reason is that the DivX 5.0.2 encoder was not fully compliant.

However I will try MP4UI and report back with the results.

DK

[bond_d9]

Originally posted by Duschkoenig
The problem seems to be that the DivX 5.0.2 converter was not fully .mp4 compliant. Seems they removed it from 5.0.3 onwards because of that reason

well the problem is that the old crappy .avi container cant really handle b-frames without hacks
now to be able to solve this problem and be able to place b-frames in avi the divx5 guys invented a hack called packed bitstream

now if you mux such packed bitstreams to mp4 you have to unpack them (as this is only an ugly hack for avi and isnt allowed in mp4 of course)

the problem was that the divx5 muxer didnt remove this hack and therefore created not spec compliant mp4 files if b-frames were used

what you can try is to remux the .mp4 file created by divx5 with the 3ivx mp4 muxer, as this muxer is maybe the best available and is also able to unpack such packed bitstreams
so if everything goes right you will get a correct .mp4 file after that, which you than can output to avi again with mp4ui for example

but still i would stay with .mp4 as its the official format of the mpeg-4 standard and much better than .avi (which needs lots of hacks as mentioned already)

[Duschkoenig]

Hi bond_d9!

Thanks a lot again! That sounds like the solution I have been looking for! I will post a reply during the next few days. Might not be before the week end since I am short of time.

I wouldn't mind staying whith the .mp4 format. However my hardware player seems to need .avi files. However, to confirm that I probably would need a compliant .mp4 file before being certain that the player can not play .mp4s. If I am successfull with correcting the non compliant .mp4s I'll try them in .mp4 format first before converting to .avi.

DK