Method for encoding Motion JPEG for PSP

[ByteMe72]

I own a PSP and have always been very keen to play my own videos on it. The existing PSP presets are great and do their job well, but their resolution is limited by the PSP’s architecture. Starting with PSP firmware 2.80 and higher, the PSP can play an additional type of video file: a Motion-JPEG file in AVI container format. It can play these at full resolution (i.e. at 480x272). There are limitations, of course. The Motion-JPEG codec is not very efficient, creating huge files. And the PSP only recognizes linear PCM audio in these files, with a setting of 22050 kHz stereo/16bit/little endian (a bitrate of around 705 kbps).

I have successfully encoded my own MJPEG files for the PSP using ffmpegX, but I do it in a very “hacked” kind of way. I extracted a copy of the ffmpeg binary from the ffmpegX application package (use the "Show Package Contents" feature of the Finder) and placed it in the /bin directory. I had to use the Terminal and the "sudo" command to do this. Placing the binary in the /bin directory allows the shell to "see" it and accept it as a command. I then use the following command-line in the Terminal to encode the video:

ffmpeg -y -i “filename.ext” -title “name for file” -vcodec mjpeg -coder 1 -bufsize 128 -s 480x272 -r 30 -b 3582 -acodec pcm_s16le -ac 2 -ar 22050 -ab 705 “output_filename.avi”

Be patient! It can take a while and all you'll see is a blur of status messages for a bit. The "filename.ext" is the name of the original file you want to encode, "name for file" doesn't seem to do much although I always use it. The frame rate can be 24 or 30 and the bitrate can be toyed with as desired, although 2860 for 24 fps and 3582 for 30 fps produces good results. I haven’t tried fractional fps (like 29.97) yet. Somebody give that a try and let us know how it turned out.

The resulting files play perfectly on the PSP (mine is currently at firmware 3.0.2). I get crisp video at full screen resolution. The price is file size: I can only get about 45 minutes of video on a 1GB memory stick! However, for short clips or half-hour TV episodes, this is the sharpest video possible on the PSP (until user-writable UMDs come along).

I know this is a kludgy way to do this, but it is the only method of encoding this new PSP format on the Mac that I know of. There are some issues (like letterboxing) that have to be handled in some other app before encoding is done (I use QuickTime Pro). If anybody out there has a different/better way of encoding videos in this format, I'm all ears!

[major]

I fail to see which benefit one would get by using MJPEG instead of MPEG4 or H264?

[ByteMe72]

There is very little to gain by using this method, other than taking full advantage of the PSP screen. Right now, as of the current (and last few) PSP firmware versions, this type of encoding is the only "legal" way to get full 480x272 resolution. The files do end up prohibitively large, and few have the resources or desire to go this route. However, for specific applications this could be of benefit to somebody so I posted it. Again, as far as I know this is the only way of doing this natively in Mac OS X that I know of (without resorting to emulation or some other bothersome trick).

I am normally quite happy with the "scaled up" video that I get from the more usual PSP video formats. However, I watch a fair amount of subtitled material and even a few extra pixels of resolution come in really handy for making those subtitles easier to read. A niche application, to be sure, but a valid one nonetheless.

Take this technique for what it's worth. Memory gets cheaper by leaps and bounds, and soon we may not care much how big these files get...

[major]

OK, I'll add this to my to-do list. Thanks for suggesting.

[Therac-25]

For what it's worth, this feature (using a variation on the above commandline right now) would be welcome for encoding video for playback on the Wii as well. Currently, the only two supported methods for video on the Wii are Motion JPEGs and FLV via the Opera Browser.

Currently trying to figure out what the limitations are on the playback for FLV on the Wii, to see if I can get something usable for a small television out of it.

[womble_timsk]

For what it's worth, this feature (using a variation on the above commandline right now) would be welcome for encoding video for playback on the Wii as well. Currently, the only two supported methods for video on the Wii are Motion JPEGs and FLV via the Opera Browser.

Currently trying to figure out what the limitations are on the playback for FLV on the Wii, to see if I can get something usable for a small television out of it.

Just wanted to add a vote from another Wii owner for implementing this feature if possible. It'd be great to be able to encode stuff onto an SD card to watch on the TV. (Of course, it'd be even better if the damned Wii could read DVDs, but that's for another forum...)

[tomlee59]

QT MoviePlayer 2.5.1 (free; and also able to display full screen, unlike later versions of QT Player), despite its name, will transcode into various formats, MJPEG being one of several. I run this on an old G3 under OS8.6, so I don't know if it will also run in Classic mode on an OSX Mac. And of course, if you have a newer mac that doesn't run classic, then you're SOL with this route. But I thought I'd mention this alternative.

I wonder if using the existing MPEG1 ffmpeg encoder would produce MJPEG output if the keyframe interval is set to 1. I've not tried to do this, so perhaps Major or someone familiar with the underlying engine would be able to answer this?