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nDs-mPeG, usually abbreviated DPG, is a special format of MPEG-1 video specifically for playback using the homebrew Moonshell program for the Nintendo DS. The video is encoded on a computer and then transferred, along with Moonshell, to the DS for playback.


[edit] Encoding

[edit] With GUI Programs

DPG files are usually created using the dpgtools program for Windows, but a newer program, BatchDPG, is a viable alternative. SUPER by eRightSoft [1]is also able to encode DPG1 files Additionally, Fengtao software has added support for the DPG1 format to its DVDFab Platinum product.

GUI encoding programs for platforms other than Windows do not exist (but see below for command-line encoding programs), but the file format is simple enough to allow DPG files to be manually encoded and placed into the proper container format. Also, a program called EZBuilder by erspicu_brox can convert to DPG with FFmpeg.

[edit] Without GUI Programs

There is a Python script which uses MEncoder and can be used on platforms where both Python and MPlayer are available. Version 0.43 of this script uses mpeg_stat which you can find here: http://bmrc.berkeley.edu/ftp/pub/multimedia/mpeg/stat/

The script can be found here. As mpeg_stat homepage is now dead, you can get it at any FreeBSD mirror, like here.

[edit] Complete List of Encoders

[edit] For Mac:

Both releases require MEncoder to be placed in the same folder.

In order to create a working DPG, one must encode it as a 15 frame/s 256*192 avi with MPEG-2 (Hi Quality) or OGG (Low Quality) 128 kps sound. A program such as MPEG Streamclip or ffmpeg can be used to do this.

While older DPG files were limited to 15 frame/s, the newer version (DPG2) supports up to 24 frame/s.

  • The Python script.

[edit] For Windows:

[edit] For Linux:

  • The Python script.

[edit] File Format

[edit] General Outline

The DPG file specification is simple. All DPG files contain a 36 byte header, followed by audio, and then a standard mpeg-1 video stream. The audio format can differ; older DPG files used a special WAV format audio, but newer versions of moonshell have phased that out in favor of MP2 audio.

The format specified below is the "DPG0" format. Moonshell supports additional versions of the DPG format[2], including DPG1, DPG2 and DPG3, though documentation of the revised formats is not included in this article at this time. DPG2 includes additional index information that allows fast relocation in the video/audio stream, thus allowing improved user navigation during playback.

[edit] File Structure

A DPG0 file begins with a 36 byte header (Note: all of the numbers below are hexadecimal.):

  • 44 50 47 30 (this stands for DPG0 in ASCII)
  • Four bytes for the number of frames in the video
  • Two bytes for the frames per second that the video runs
  • 00 00
  • Four bytes for the audio sample rate
  • 00 00 00 00 (this was the number of audio channels, now deprecated in favor of MP2 audio)
  • 24 00 00 00 (this is the start of the audio file, i.e. right after the header)
  • Four bytes for the length, in bytes, of the audio
  • Four bytes for the above length + 36 bytes (i.e. the start of the video file)
  • Four bytes for the length, in bytes, of the video

(A C program and source is included in the BatchDPG source code to simplify the header generation)

After a header has been made, concatenate everything together:

  • Linux & Mac OS X (Terminal.app): cat header.head audio.mp2 video.raw.mpg > ndsmpeg.dpg
  • Windows: copy /b header.head + audio.mp2 + video.raw.mpg ndsmpeg.dpg

[edit] Audio Encoding

The audio is encoded in standard MP2 format. For example, using ffmpeg to encode in.avi into out.mp2 at a 22050 sample rate and a bitrate of 64 kbit/s:

 ffmpeg -i in.avi -vn -ab 64k -ar 22050 out.mp2

[edit] Video Encoding

MoonShell can be very particular about the types of MPEG video it will decode correctly. Videos made with ffmpeg do not work very well; MEncoder seems to be a better option. The FPS and bitrate rely on personal preference, but the DS does not have much processing power - lower bitrates and framerates seem to work better. Finally, since the DS screen is so small, rescaling to 256 by 192 is the most space-efficient.

Here is an example command using MEncoder (this should be on one line):

 mencoder in.avi -o out.mpg -nosound -ovc lavc -lavcopts vcodec=mpeg1video:vrc_buf_size=327:vrc_maxrate=512:vbitrate=256:vstrict=-1 -ofps 18 -vf scale=256:192

This produces an AVI with a working MPEG video stream, but it should be extracted into a raw format with ffmpeg, however, this is not required:

 ffmpeg -i out.mpg -an -vcodec copy -f mpeg1video out.raw.mpg

Or, in more recent versions of mencoder you can just add the following option:

 -of rawvideo

This makes MEncoder output raw video with no need to extract it later with ffmpeg.

[edit] Versions

[edit] DPG0

Mono audio was used

[edit] DPG1

Added stereo sound

[edit] DPG2

GOP List added for faster seeking

[edit] DPG3

Ability to choose OGG as audio format.
Better video Quality

[edit] DPG4 (MoonShell 2.00)

Audio bitrate is 160KB/s
Video Quality is slightly improved (TESTED: Video bitrate at 800+KB/s without skipping).

[edit] External links

[edit] References

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