nvid2

new ti nspire video player using ndless + MPEG-4 Part 2 codec
inspired by the older project nvid

Current state: Only CX-II compatible, HW-W+
Includes the II-T and CAS models

Uses a stripped down version of xvid as the video decode library.

ffmpeg command:
ffmpeg -i YOUR_VIDEO.extension -map 0:0 -c:v libxvid -bf 0 -gmc 0 -pix_fmt yuv420p -vf "scale=320:240,fps=24" -me_quality 6 -mbd rd -trellis 1 -b:v 500k -f m4v YOUR-VIDEO.tns

Since the display on the CX-II is rotated 90 degrees, pre-rotating the video skips needing to rotate the decoded output at runtime. This can save ~3.2ms per frame at 16bpp.

Use the option -prv to tell the player that the video is pre-rotated.

For a clockwise 90° rotation, use FFmpeg's transpose=1 and swap the scale to 240x320:

ffmpeg -i YOUR_VIDEO.extension -map 0:0 -c:v libxvid -bf 0 -gmc 0 -pix_fmt yuv420p -vf "transpose=1,scale=240:320,fps=24" -me_quality 6 -mbd rd -trellis 1 -b:v 500k -f m4v YOUR-VIDEO.tns

Then play it with -prv and Nmfb (The magic framebuffer is no longer needed for hardware rotation):

play YOUR-VIDEO.tns -Nmfb -prv

Notes:

• -prv expects the encoded dimensions to be 240x320 (width x height). If you feed it 320x240, it will error.
• transpose has multiple modes; if transpose=1 rotates the “wrong way” for your source, adjust the transpose mode accordingly.

• -map 0:0: the video stream is usually the first input stream, choose something else if ffprobe says something different
• -c:v libxvid: uses the libxvid encoder for mpeg4 part 2 video. the project uses the xvid decoder
• -bf 0: disables b-frames, easier on the decoder
• -gmc 0: global motion compensation, harder on the decoder when on
• -pix_fmt yuv420p: format should be easier on the decoder
• -vf "scale=320:240,fps=24": the ti-nspire's display is 320x240, setting the resolution exactly removes the need for filtering on-device. set the fps to any value you like
• -me_quality 6: increases motion estimation effort to max. this increases encoder efficiency at the expense of encode time, while minimally affecting decode effort. since mpeg4 part 2 is such an old codec, the maximum setting is still very easy for modern computers to handle.
• -mbd rd: macroblock decision mode, same explanation as above
• -trellis 1: quantization, same explanation as above
• -b:v 500k: sets the video bitrate to average 500 kbps. a minute of video would then be around 3.75 MB. this number can be increased or decreased, depending on your target quality
• -f m4v: sets the file format as an elementary mpeg4 part 2 stream, required.

Opening nvid2 will place you into a terminal-like interface with 3 commands:

• ls: list stuff in directory
• cd: change directory
• play: play a video file (the thing you encoded with ffmpeg)

When playing a video, you can press esc to stop.

Usage:

• play <filename> [options...]

Flags (later flags override earlier ones):

• -b: benchmark mode (no video output)
• -bdb: blit frames even in benchmark mode

Output / framebuffer mode:

• -mfb: use the magic framebuffer to perform rotation (default: on)
• -prv: pre-rotated video (no rotation during blit; video must be pre-rotated to 240x320)

Decode quality / latency:

• -fd: fast decoding (default: on) (lower CPU usage, lower quality)
• -ld: low-delay mode (default: on) (reduces latency; disables b-frame support)
• -dbl / -dbc: enable luma / chroma deblocking filter
• -drl / -drc: enable luma / chroma deringing filter

Turning off defaults:

• Any option that is on by default can be disabled with the opposite flag form: -N... (example: -Nmfb disables the magic framebuffer).

Incompatibilities enforced by the player:

• -mfb cannot be combined with -prv, that wouldn't logically make sense

Examples:

• Normal playback (defaults): play video.tns
• Benchmark decode only: play video.tns -b
• Benchmark but still show frames: play video.tns -b -bdb
• Pre-rotated playback (skip rotation work): play video.tns -Nmfb -prv
• All deblock + dering filters (very slow): play video.tns -dbl -dbc -drl -drc

• b frames are not supported. The decode loop does not support the extra logic required for B-frames. This may change in the future.
• you can use ffmpeg's native mpeg4 encoder if you want, but it likely has a different set of flags
• if you set the output file's file extension as *.m4v, the container format will change and decoding will fail. the -f flag makes it a raw stream, *.tns isn't recognized by ffmpeg so it ignores it
• try out a two pass decode on your video
• all the budget went to the video player architecture, the ui is horrendous. anyone is free to contribute a nicer ui or create a fork

Currently, 30 fps and above is quite easily achievable, better than the older nvid which used the more complex vp8 codec. 60 fps realtime is possible when overclocked at ~456MHz CPU, 228MHz APB, using a pre-rotated video encoded with MPEG-4 Part 2 SP (Simple Profile, no qpel, gmc, b-frames).

nvid2 is licensed under the GNU General Public License, version 2 or (at your option) any later version (SPDX-License-Identifier: GPL-2.0-or-later).

nvid2 includes modified source code from the Xvid MPEG-4 video codec, which is also licensed under GPL-2.0-or-later.