vopus9 - The No-Bullshit VP9/Opus Encoder

What the heck is this?

vopus9 is a command-line tool that takes your videos and turns them into modern, efficient MKV files with VP9 video and Opus audio. Think of it as a "set it and forget it" encoder for your movie collection.

Why should I care?

• VP9 - Google's codec that's as good as H.265 but without the patent headaches
• Opus - The audio codec that just works, sounding great even at low bitrates
• MKV - The container that eats everything (subtitles, multiple audio tracks, chapters, you name it)

And the best part? It handles all the boring stuff automatically. Resolution detection? Check. Multi-channel audio? Check. Recursive batch processing? You bet.

Installation (the quick version)

First, grab the dependencies:

# Ubuntu/Debian

sudo apt install ffmpeg mediainfo

# macOS

brew install ffmpeg mediainfo

# Windows - download ffmpeg and mediainfo, add to PATH, cry a little

Then compile the beast:

git clone https://github.com/philtems/vopus9

cd vopus9

cargo build --release

sudo cp target/release/vopus9 /usr/local/bin/

Basic usage (the "I just want this to work" version)

# Encode a single file with automatic settings

vopus9 -i my_video.mp4

# That's it. Seriously. It'll figure out the rest.

The output will be my_video_0001.mkv sitting right next to your original file.

All the knobs and buttons (aka command-line options)

Input / Output

---

-i <file> Input video file -I <directory> Input directory (encode everything inside) -r Recursive mode (go into subfolders) -o <file> Output file name (adds _0001 if exists) -O <directory> Output directory (keeps folder structure with -r)

---

Quality Control

---

--crf <value> Quality-based encoding. Lower = better. Auto or 8-48. -bv <value> Target bitrate. Auto, XK (e.g., 1500K), or XM (e.g., 2M) -ba <value> Audio bitrate. Auto or XK (e.g., 128K)

---

Speed vs Quality

---

-speed fast Fast Acceptable Daily use (default) -speed medium Medium Good When you care a bit -speed low Slow Excellent When size matters more than time

---

Handy extras

---

--info Just show file info, don't encode anything --delete Delete source after successful encode, rename output to original name --rename Rename source to _old_original, output takes original name

---

How the magic works

Auto quality (because you're lazy, and that's ok)

Based on resolution:

---

< 720p 34 1.0 Mbps 720p 32 1.5 Mbps 1080p 28 3.0 Mbps 4K 20 12.0 Mbps

---

But wait, there's more! It actually uses pixel count, not just height. So a weird 1920x800 video gets treated differently from proper 1920x1080. Smart, huh?

Audio auto-bitrate (because math is hard)

---

1-2 (stereo) 128 kbps 3-5 256 kbps 6-7 (5.1) 384 kbps 8+ (7.1) 512 kbps

---

Encoding speeds demystified

• Fast (-deadline realtime -speed 6): Good enough for most stuff, pretty quick
• Medium (-deadline good -speed 6): Better quality, takes longer
• Low (-deadline good -speed 4): The "I have all night" mode

Real-world examples

That one movie you want to keep forever

vopus9 -i "Interstellar.2014.1080p.mkv" --crf 22 -speed medium

Quality will be almost indistinguishable from the original, but the file will be much smaller.

Your entire TV series collection

vopus9 -I ~/TV_Shows -r -O ~/Encoded_TV_Shows

Grab a coffee. Or twelve. This might take a while.

Old stuff you don't really care about

vopus9 -i "home_video_2005.avi" --crf 34 -speed fast

Small files, decent quality. Perfect for "I might watch this again someday".

Replace originals (brave mode)

vopus9 -i video.mp4 --delete

Encodes, then deletes the original and renames the output to video.mp4. No leftovers, no clutter.

Safe replacement (paranoid mode)

vopus9 -i precious_video.mkv --rename

Original becomes _old_precious_video.mkv, encoded version takes the original name. You can delete the old one later when you're sure the new one works.

Just tell me what's inside

vopus9 -i mysterious_file.mkv --info

Shows resolution, duration, audio tracks, subtitles... everything except the kitchen sink.

What gets preserved (spoiler: almost everything)

• All audio tracks (with their languages and titles)
• All subtitle tracks
• Chapters (if they exist)
• HDR metadata (Dolby Vision, HDR10+)
• Original stream order (no weird rearrangements)

Each audio track gets its own bitrate based on channel count. A French stereo track? 128k. An English 5.1 track? 384k. Smart, right?

Pro tips

The "I have a life" batch encoding

nohup vopus9 -I ~/Videos -r -O ~/Encoded -speed fast > encode.log 2>&1 &

Run it in the background and go to sleep. You'll wake up to smaller videos.

Check your progress

The progress bar shows:

• Percentage done
• Time elapsed / total duration
• Encoding speed (1.0x = real-time, 2.0x = twice as fast)
• ETA (because waiting is suffering)
• Current bitrate
• Estimated final size

Speed expectations

On a modern CPU:

• 1080p: ~1.5-2.5x real-time (a 2-hour movie takes ~1 hour)
• 4K: ~0.3-0.8x real-time (a 2-hour movie takes 2.5-6 hours)

Yes, VP9 is slow. No, there's no GPU acceleration (the quality isn't as good anyway).

Troubleshooting (when things go sideways)

"ffmpeg not found"

Install ffmpeg. The tool doesn't bundle it.

"mediainfo not found"

Install MediaInfo. It's needed to read file metadata.

"Duration not found"

Your file might be corrupted or in a weird format. Try running mediainfo manually to see what's up.

The output bitrate seems wrong

The displayed bitrate during encoding is an average over the whole file. It'll stabilize after the first minute or so.

Subtitles are out of sync

Subtitles are copied without modification. If they were broken in the source, they'll stay broken.

The fine print

• No GPU encoding (CPU only, for quality reasons)
• No 2-pass encoding (1-pass is good enough for most uses)
• Image-based subtitles (PGS, VobSub) are copied, not converted
• Windows users: paths with spaces need quotes, like everywhere else

Author

Philippe TEMESI - https://www.tems.be

That's it. Go encode some videos. Or don't. I'm not your mom.