AV1 to MKV Converter

Convert AV1 to MKV: What This Tutorial Covers

A .av1 file is a raw AV1 elementary stream — just the compressed video bitstream, with no container, no seek index, and no audio. Most players and every browser refuse to open a bare .av1, so it sits there unplayable. This guide wraps that stream into an MKV (Matroska) file you can play and scrub in VLC, MPV, Kodi, or Plex, and explains the one setting that decides whether your modern AV1 survives intact or gets re-encoded down to an older codec.

Why a Raw .av1 Stream Needs a Container

When an encoder such as aomenc, an FFmpeg test build, or a hardware capture pipeline writes a raw .av1 file, it emits only the coded picture data — Open Bitstream Units (OBUs), one after another. There is no index telling a player where each frame begins, no duration, and — because AV1 is a video-only codec — no audio. A player has nothing to seek against, which is why a bare stream usually will not scrub or even open. Wrapping it in a container adds the frame index, timestamps, and track structure a player needs, so the same video that would not play before opens and seeks cleanly afterward.

MKV (Matroska) is a strong target for this. It is an open container, standardized in 2002 and built on EBML (Extensible Binary Meta Language), and it can carry AV1 natively: the Matroska specification assigns AV1 the codec ID V_AV1, so the stream can go in as-is without being re-encoded. MKV also holds an effectively unlimited number of video, audio, subtitle, and chapter tracks, which is why VLC, MPV, Kodi, Plex, and most modern smart TVs treat it as a first-class format. 1

How to Convert AV1 to MKV

1. Upload Your AV1 File: Drag and drop your .av1 file onto the page or click "+ Add Files". You can queue several raw streams and convert them in one batch with the same settings.
2. Set the Video Codec: Open Advanced Options and choose under Video Codec. MKV output defaults to H.264 (a re-encode); select AV1 instead to keep the original stream inside the MKV container with no quality loss.
3. Adjust File Compression (optional): Under File Compression the Quality Preset defaults to "Very High (Recommended)"; switch to Constant Quality, Constant Bitrate, or Specific file size if you have a size target, and use Time Range under Trim to keep only part of the clip.
4. Convert and Download: Click Convert and download your MKV. No sign-up, no watermark.

Walk-through: Keep AV1 or Re-encode to H.264?

The Video Codec dropdown is the choice that matters most on this page, because MKV's default here is not AV1 — it is H.264. That is the opposite of a clean wrap, so it is worth understanding before you click Convert:

• Keep it as AV1 (select AV1): the existing coded video is wrapped into MKV with no re-encoding and no generational quality loss. This is the fastest, highest-fidelity path and the right pick when you just need an encoder's output to become a seekable, playable file — for example checking an aomenc test build, or archiving an elementary stream at full efficiency. AV1 stays AV1.
• Re-encode to H.264 (the MKV default): if you leave the default, the AV1 video is decoded and encoded again as H.264. Because you are converting a newer, more efficient codec back to an older one, quality can only drop at a given file size, and the file gets larger for the same picture — H.264 is roughly a generation behind AV1 in efficiency. The upside is that H.264 plays on almost anything, including old hardware that cannot decode AV1. Pick this deliberately for maximum device reach; do not pick it by accident. H.265, VP9, MPEG-4 and others are also offered.
• Audio stays empty either way: because the .av1 source carries no sound, MKV defaults its audio codec to AAC but has nothing to put in it, so the output is silent. That is expected for a raw AV1 source, not a fault. Mux in a matching audio file afterward if you have one.

Common Errors and How to Fix Them

• "The MKV has no sound" — Correct and unavoidable from a raw .av1 source: the stream is video-only, so there is no audio to carry. Add an audio track separately if you have one.
• "The file looks bigger / softer than the original AV1" — You almost certainly left the default H.264 codec, which re-encodes. Re-run with Video Codec set to AV1 to wrap the stream losslessly instead of transcoding it.
• "It won't play in my old player or on a smart TV" — Older players and some TVs lack an AV1 decoder even though they open MKV fine. Re-run with the Video Codec set to H.264 for the broadest hardware compatibility.
• "AV1 plays but stutters above 1080p" — Without an AV1 hardware decoder the player falls back to software decode, which is CPU-heavy; either enable hardware decoding in your player or re-encode to H.264 for smoother playback on that machine.
• "Conversion failed / file rejected" — A truncated or partially written .av1 capture may lack a valid stream header; re-export the file from the encoder before retrying.

When This Doesn't Work

This tool expects a genuine raw AV1 elementary stream. If your file is actually an MKV or MP4 that was renamed to .av1, it already has a container and you want a remux of that file instead. AVIF is also not handled here — that is the still-image format built on the AV1 codec, not a video stream. DRM-protected or encrypted streams cannot be converted by any tool until the protection is removed at the source. And if the stream itself is corrupt — a dropped capture or an interrupted encode — no container can repair the missing frames; you will need to re-create the .av1 file from the original source.

Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public.

Frequently Asked Questions

Does converting AV1 to MKV re-encode the video or just rewrap it?

It depends on the Video Codec you pick, and the default matters here. MKV output defaults to H.264, which decodes and re-encodes your AV1 — costing quality and growing the file because H.264 is less efficient. Select AV1 instead and the existing stream is wrapped into MKV with no re-encoding and no quality loss. If your goal is to keep the original AV1 intact, change the dropdown to AV1 before converting.

Why is my MKV silent after converting from AV1?

Because a .av1 file is a video-only elementary stream — it never contained audio in the first place, so there is nothing to carry into the MKV. The container defaults its audio codec to AAC, but with no source audio the output stays silent. This is normal for a raw AV1 stream. If you need sound, mux a separate audio file into the MKV afterward.

Does MKV actually support AV1, or do I have to re-encode?

MKV supports AV1 natively. The Matroska specification defines an AV1 mapping under the codec ID V_AV1, and players including VLC (since version 3.0) and MPV decode AV1-in-MKV directly. So you can keep an AV1 stream in MKV at full efficiency rather than transcoding it — you just have to select AV1 on this page, because the default codec for MKV output is H.264. 1

Will AV1 inside MKV play on my TV or media player?

On the desktop, yes — VLC, MPV, Kodi, and Plex play AV1-in-MKV, and browsers that play AV1 cover roughly 93% of users. But many older smart TVs and set-top boxes can open MKV without having an AV1 hardware decoder, so they may show a black screen or fall back to choppy software decode. For those devices, re-run with the Video Codec set to H.264, or use the AV1 to MP4 converter for the most widely compatible container-plus-codec pairing. 2

In our testing, does choosing AV1 actually avoid a re-encode?

In our testing, selecting AV1 as the Video Codec on a clean raw .av1 stream produces an MKV whose video matches the source frame-for-frame, with no transcode step — the conversion finishes quickly and the picture is identical to the input. Leaving the default H.264 triggers a full re-encode that takes longer and visibly softens fine detail at the same file size, because the newer codec is being converted back to an older one.

What is the .av1 file extension, exactly — and is it the same as AVIF?

A .av1 file is a raw AV1 (AOMedia Video 1) video bitstream with no container around it — the form encoders and test pipelines emit before the video is muxed into MKV, WebM, or MP4. AV1 is a royalty-free video codec from the Alliance for Open Media, finalized in 2018 and roughly 30% more efficient than VP9 at the same quality. AVIF is a different thing: a still-image format that uses the same AV1 coding, so it is not what this video converter produces. If you only need the stream playable in a browser instead, AV1 to WebM targets the web container. 3