Batch video compressor and audio/video converter. Version 1.0.0.
Nothing happens on its own. Presets only fill in settings, and no checkbox is ticked for you. Work starts when you press Start.
Both versions share the same screen, settings and preset files. They differ in where FFmpeg runs.
| Online (jeffapierson.com) | PC version (Windows) | |
|---|---|---|
| Engine | FFmpeg built for the browser (WebAssembly) | The full FFmpeg program installed on your PC |
| Your files | Read straight from your disk inside the browser tab. Never uploaded. | Never leave your PC |
| Speed | About 3 to 10 times slower. Multi-thread when the browser allows it. | Full speed, several files at once, graphics card encoding |
| Size limits | Finished files are held in memory; keep each under about 2 GB | No practical limit |
| Formats | H.264, H.265, ProRes, GIF, WebP, and MP3, AAC, Vorbis, WAV, FLAC, AIFF and ALAC. AV1, VP9 (WebM) and Opus are PC only, because they stall or crash in the browser build of FFmpeg. | Everything, plus AV1 and graphics card encoders (Intel Quick Sync, NVIDIA, AMD) when the PC has them |
| Saving | Download, ZIP, or Save All to Folder (Chrome and Edge) | Written straight to disk next to the original or into a folder you pick |
| Best for | Quick jobs, audio, short clips, other people | Big batches, long videos, AV1 and H.265 |
The top of the page shows which engine is running, for example Online · multi-thread (4) or PC version · FFmpeg 7.1 · graphics card: Intel Quick Sync.
Online, the first visit downloads FFmpeg itself (about 31 MB); after that the browser keeps it. Add ?single to the address to force the single-thread engine if a multi-thread run ever stalls.
Makes videos smaller. The most savings come from the resolution and the bitrate.
| Choice | What it does | Use it when |
|---|---|---|
| Target file size | Works out the bitrate from the length so the file lands at the size you type (in MB, where 1 MB = 1,048,576 bytes). A 3% allowance is kept for the file structure. | Email (25 MB), messaging (10 MB), upload limits |
| Quality | Keeps the look steady and lets the size vary. High, Balanced and Small match CRF 20, 23 and 28 for H.264. | Archiving, YouTube, anything without a size limit |
| Percent of original | Aims for that share of the original size, for example 50%. | "Make it half as big" |
| Quality with a bitrate limit | Quality mode that never goes over the limit you type (kbps). | Platforms with a maximum bitrate |
Accuracy (target and percent, PC version): Two-pass reads the video once to plan, then writes it, so the size lands close to the target. It takes about twice as long. One-pass is faster and the size is approximate. Graphics card encoders and AV1 always use one pass. The online version always uses one pass with a bitrate ceiling, because two-pass encoding stalls in the browser build of FFmpeg; sizes usually land within a few percent under the target.
A one-minute 1080p phone video of about 120 MB usually comes out at 30 to 40 MB with H.264 Balanced, 15 to 20 MB at 720p, and 18 to 25 MB with H.265. Real results depend on the picture: busy scenes need more data than a person talking.
If a target is too small for the length, the file will not run and the Estimate column says why. If it will look blocky, you get a warning sign with a suggestion. If a "compressed" file comes out larger than the original (common for videos that were already well compressed), it is marked Check and the note says the original is the better file. Nothing is deleted either way.
Same options as Compress, set up for changing the format instead of the size. It starts in Quality mode (High). Extra choices under Make:
Takes audio files, or the sound from video files, to another audio format.
| Format | Type | Use it for |
|---|---|---|
| MP3 | Lossy | Plays everywhere. 192 kbps for music, 96 kbps mono for speech. VBR V0 to V2 gives the best quality per MB. |
| AAC (.m4a) | Lossy | Apple, podcasts, video soundtracks. Slightly better than MP3 at the same bitrate. |
| Opus | Lossy | Best quality at low bitrates (voice at 32 to 64 kbps). Always plays at 48 kHz. |
| OGG Vorbis | Lossy | Games and older web players. |
| WAV | Uncompressed | Editing. 16-bit, 24-bit or 32-bit float. Files over 4 GB switch to RF64 automatically. |
| FLAC | Lossless | Archiving at about half the size of WAV with no quality loss. |
| AIFF | Uncompressed | Mac users who want WAV-style files. |
| ALAC (.m4a) | Lossless | Apple Music and iTunes libraries. |
Make it this loud measures each file's loudness first, then changes the level in a second pass so it lands on the target, with a peak limit (-1 dBTP by default). The result notes say how loud the file was and how much it changed.
| Target | Where it is used |
|---|---|
| -14 LUFS | Spotify, YouTube, most streaming |
| -16 LUFS | Podcasts (Apple, most hosts) |
| -19 LUFS | Quieter spoken word, mono podcasts |
| -23 LUFS | European broadcast (EBU R128) |
| -24 LUFS | US television (ATSC A/85) |
The level is changed as one steady gain (no pumping) whenever the peak limit allows; very dynamic files fall back to gentle automatic levelling. Off keeps the original level exactly.
Pulls the sound out of video files. Copy the original sound is fastest and changes nothing (AAC comes out as .m4a, MP3 as .mp3, Opus as .opus, and so on). Convert to a format uses the same options as Convert audio, including loudness. The Transcript-ready preset makes 16 kHz mono WAV for speech-to-text tools.
Moves the picture and sound into a new file type without re-encoding, so it takes seconds and loses nothing. Typical uses: MKV to MP4 for phones and editors, or MP4 to MOV. Subtitles are converted to the type MP4 and MOV need. If a track cannot go in the new type (for example AAC sound into WebM), the file fails with FFmpeg's reason and nothing else is touched. Use Convert video in that case.
clip_small.mp4. Existing files are never replaced: a number is added, as in clip_small (2).mp4..partial in its name; it gets its real name only after it passes the checks. If a file is cancelled or fails, the half-written .partial file is left where it is and its path is shown, so you can delete it yourself.Every finished file is read back before it counts as done. The check confirms it opens, has a picture and sound where expected, and has the same length as the original (within 1% or 0.6 seconds). A tick ✓ next to the name means it passed.
| Status | Meaning |
|---|---|
| Done | Finished and passed the checks. |
| Check | Finished, but read the note: larger than the original, over the target size, or a check did not pass. |
| Failed | FFmpeg stopped with an error. The reason is shown; Log has the details. |
| Skipped | The settings do not fit this file (for example Compress video on an MP3). |
| Cancelled | You stopped it. It can run again. |
Each tab has built-in presets (Email, Messaging, Podcast, Archive and more). Picking one fills in the settings; it never starts anything and never turns on extra processing beyond what it lists. Presets... saves your own, deletes them, and exports or imports a .scpreset file. The same file works in the online and PC versions.
| Goal | Use |
|---|---|
| Send by email | Compress video, preset Email (H.264 MP4, 720p, 25 MB) |
| Text or Messenger | Preset Messaging (10 MB) |
| Facebook, Instagram | Preset Facebook / Instagram (H.264 MP4, 1080p, 30 fps, 5 Mbps limit) |
| Keep a smaller archive copy | H.265 MP4 Balanced, or AV1 on the PC version |
| Put video on a web page | H.264 MP4, or VP9 WebM |
| Edit in Premiere, Resolve or Final Cut | ProRes 422 MOV, and WAV 24-bit for sound |
| Podcast episode | MP3 96 kbps mono at -16 LUFS (preset Podcast) |
| Music master for streaming | WAV 24-bit at -14 LUFS, or FLAC |
| Phone video won't open in an editor | Change container (MKV to MP4), or Convert video to H.264 MP4 |
StudioConverter-1.0.0.zip from the StudioConverter page and unzip it.install.cmd. It installs FFmpeg and a private copy of Python with winget and uv if they are missing, copies StudioConverter to %USERPROFILE%\StudioConverter, and adds StudioConverter to the Start menu and desktop. It never deletes anything; a reinstall keeps your settings and saves a backup of the old program file.http://127.0.0.1:8740 in your browser. Only this PC can reach it.The engine keeps running in the background after you close the tab; open the shortcut again to get back to it. Stop PC engine (top right) closes it. Settings, logs and the unfinished-batch record live in the data folder inside the program folder. Two-pass log files collect in data\work; they are small and can be deleted by hand.
| Problem | Fix |
|---|---|
| Online: "FFmpeg did not start" | Use a current Chrome, Edge, Firefox or Safari. Reload the page. Corporate filters can block the 31 MB engine file. |
| Online: a file stalls at the same percent | Cancel it, add ?single to the address, and run it again. Long or 4K files are better on the PC version. |
| Online: "Very large output" warning | The browser holds finished files in memory. Lower the resolution, split the batch, or use the PC version. |
| "won't run" in the Estimate column | Hover the warning sign for the reason, such as a target too small for the length, or a sound type that cannot be copied into WebM. |
| File is larger than the original | The original was already well compressed. Lower the quality or resolution, or keep the original. |
| Over the target size | Use Two-pass, or lower the target a little. Very short clips and graphics card encoders overshoot more. |
| PC: the page does not open | Open http://127.0.0.1:8740 by hand. If another program uses that port, StudioConverter uses the next free one up to 8749. |
| PC: "FFmpeg was not found" | Run install.cmd again, or put the path to ffmpeg.exe and ffprobe.exe in data\config.json as {"ffmpeg": "C:\\path\\ffmpeg.exe", "ffprobe": "C:\\path\\ffprobe.exe"}. |
| PC: no graphics card choice | The engine tests Intel Quick Sync, NVIDIA and AMD when it starts and only lists the ones that work. Update the graphics driver and restart the engine. |
| PC: Add Files does nothing | The file window may be behind the browser. Check the taskbar. |
| Bitrate | How much data each second of video or sound uses (kbps). More bitrate, larger file, better quality. |
| Codec | The method that compresses the picture or sound (H.264, AAC). The container is the file type that holds them (MP4, MKV). |
| CRF | Constant Rate Factor, a quality setting. Lower numbers mean higher quality and larger files. |
| Two-pass | Reading the video twice so a target size can be hit closely. |
| Remux | Moving tracks into a new container without re-encoding them. |
| LUFS | Loudness units relative to full scale, the standard measure of how loud audio sounds. |
| dBTP | True peak in decibels, the highest point of the waveform including between samples. |
| Lossless | Compressed with no change to the sound (FLAC, ALAC). Lossy formats (MP3, AAC, Opus) throw away detail you are unlikely to hear. |
| Quick Sync, NVENC, AMF | The video encoders built into Intel, NVIDIA and AMD graphics. |
© 2026 Jeff A Pierson · jeffapierson.com · StudioConverter uses FFmpeg (LGPL/GPL), which is the property of its authors.