PL_MPEG - MPEG1 Video decoder, MP2 Audio decoder, MPEG-PS demuxer

MPEG1 Decode library for Dreamcast Ver 2.0

• Originally ported by Tashi 2023/09/19
• Currently maintained by Andy Barajas (https://github.com/andressbarajas)

FEATURES

• MPEG1 video playback with MP2 audio (mono or stereo)
• Supports video resolutions up to 640x480
• Configurable cancel buttons during playback (controller buttons, keyboard keys, button combos)
• Simple, extended, and manual playback APIs
• Overridable memory allocators and file I/O

ENCODING FOR DREAMCAST

Videos must be MPEG-PS (.mpg) with MPEG1 video and MP2 audio. Use constant bitrate (-minrate/-maxrate/-bufsize matching -b:v) to avoid decode spikes that cause frame drops. Audio at 32kHz keeps CPU overhead low while sounding good.

Disclaimer: I’ve validated these encode settings using in-memory playback (romdisk). I haven’t yet verified them with CD streaming, so results may differ. If you see lag/stutter when playing from disc, please let me know.

320x240 (4:3) — Standard (Recommended Standard):

ffmpeg -i input.mp4 -vf "fps=24,scale=320:240" -c:v mpeg1video -b:v 1500k -minrate 1500k -maxrate 1500k -bufsize 1500k -ac 2 -ar 48000 -c:a mp2 -b:a 128k -f mpeg 320x240.mpg

368x208 (16:9) — Widescreen (Recommended Widescreen):

ffmpeg -i input.mp4 -vf "fps=24,scale=368:208" -c:v mpeg1video -b:v 1500k -minrate 1500k -maxrate 1500k -bufsize 1500k -ac 2 -ar 48000 -c:a mp2 -b:a 128k -f mpeg 368x208.mpg

448x336 (4:3) — Standard:

ffmpeg -i input.mp4 -vf "fps=24,scale=448:336" -c:v mpeg1video -b:v 1100k -minrate 1100k -maxrate 1100k -bufsize 1100k -ac 2 -ar 32000 -c:a mp2 -b:a 128k -f mpeg 448x336.mpg

512x288 (16:9) — Widescreen:

ffmpeg -i input.mp4 -vf "fps=24,scale=512:288" -c:v mpeg1video -b:v 1100k -minrate 1100k -maxrate 1100k -bufsize 1100k -ac 2 -ar 32000 -c:a mp2 -b:a 128k -f mpeg 512x288.mpg

For mono audio, replace -ac 2 -b:a 128k with -ac 1 -b:a 64k.

LICENSE

pl_mpeg.h - MIT LICENSE mpeg.c, mpeg.h - Public Domain

THANKS TO

Dominic Szablewski (https://phoboslab.org) - Great decoding engine. Provided advice and ideas:

• Ian Robinson (https://github.com/ianmicheal)
• Jnmartin84 (https://github.com/jnmartin84)
• BitBank2 (https://github.com/bitbank2)
• Falco Girgis (https://github.com/gyrovorbis)

with permission https://dcemulation.org/phpBB/viewtopic.php?p=1060259#p1060259

Single-file MIT licensed library for C/C++

See pl_mpeg.h for the documentation.

Why?

This is meant as a simple way to get video playback into your app or game. Other solutions, such as ffmpeg require huge libraries and a lot of glue code.

MPEG1 is an old and inefficient codec, but it's still good enough for many use cases. All patents related to MPEG1 and MP2 have expired, so it's completely free now.

This library does not make use of any SIMD instructions, but because of the relative simplicity of the codec it still manages to decode 4k60fps video on a single CPU core (on my i7-6700k at least).

Example Usage

• pl_mpeg_extract_frames.c extracts all frames from a video and saves them as PNG.
• pl_mpeg_player.c implements a video player using SDL2 and OpenGL for rendering.

Encoding for PL_MPEG

Most MPEG-PS (.mpg) files containing MPEG1 Video ("mpeg1") and MPEG1 Audio Layer II ("mp2") streams should work with PL_MPEG. Note that .mpg files can also contain MPEG2 Video, which is not supported by this library.

You can encode video in a suitable format using ffmpeg:

ffmpeg -i input.mp4 -c:v mpeg1video -c:a mp2 -format mpeg output.mpg

If you just want to quickly test the library, try this file:

https://phoboslab.org/files/bjork-all-is-full-of-love.mpg

Limitations

• no error reporting. PL_MPEG will silently ignore any invalid data.
• the pts (presentation time stamp) for packets in the MPEG-PS container is ignored. This may cause sync issues with some files.
• no seeking.
• bugs, probably.