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The file is usually fine; the player is missing a decoder for the picture or the sound. Find out which one, then pick the right fix.
“Video codec not supported” means the player opened the file but has no decoder for the way the picture inside it was compressed; “audio codec not supported” means the same for the sound. The file itself is almost never damaged. The fix is to find out which stream is the problem and then either play it with something that has the right decoder or make a copy in H.264 video with AAC audio, the pairing nearly every device can play.
The usual culprits are HEVC (H.265) on Windows PCs without Microsoft’s HEVC extension, AV1 on older phones and computers, Apple ProRes anywhere outside Apple and editing software, 10-bit H.264, and Dolby (AC-3, E-AC-3) or DTS surround sound on phones and in browsers. An MP4 or MKV can hold any of them, so the file name won’t tell you which.
To see what is inside without playing it, check the codec here: open the file and the Video and Audio sections name both codecs, with a Plays on row for a quick compatibility read. The file stays on your device. metadata.video reads and explains files; it doesn’t convert them, so the conversion options further down use free desktop tools.
Work through these in order; most people are done by step 3.
If you hear sound over a black picture, the video codec is the problem; if the picture plays in silence, it is the audio. To name the codec, on a Mac open the file in QuickTime Player and choose Window > Show Movie Inspector (Command-I); in VLC on Windows choose Tools > Codec Information (Ctrl+J).
VLC plays almost every codec without relying on the system, on Windows, Mac, Android and iPhone. If it plays there, the file is fine and only your usual player is missing a decoder.
For HEVC, install HEVC Video Extensions from the Microsoft Store; for AV1, install the free AV1 Video Extension. Then reopen the file in Media Player or Photos.
On an iPhone, open Settings, tap Camera, tap Formats and choose Most Compatible so new videos are saved as H.264. Switch back to High Efficiency when you want smaller files again.
Use a converter such as HandBrake, VLC’s Media > Convert/Save (Ctrl+R) or ffmpeg to make an MP4 with H.264 video and AAC audio. Keep the original, since every conversion loses a little quality.
A video file is a container holding separate streams. Each stream is compressed with its own codec, and a player has to decode every stream it wants to play. An error message rarely says which one it choked on, so start from the symptom.
| What you see | Most likely cause | Where to look |
|---|---|---|
| Sound plays over a black or frozen picture | The video codec (often HEVC, AV1, ProRes or 10-bit H.264) | Codec, profile and bit depth in Video |
| Picture plays with no sound, or an “audio codec not supported” message | The audio codec (often AC-3, E-AC-3 or DTS) | Codec and channels in Audio |
| The file won’t open at all, or the app says the format is unsupported | The container (MKV, AVI, MTS) or both streams | The summary and key facts in Overview |
| Plays on a computer but not on a TV from a USB stick | The TV’s decoder limits: codec, level, bit depth or audio format | Profile, level and audio codec |
| HEVC file plays in VLC but not on an iPhone or Mac | The hev1 codec tag instead of hvc1 | Codec tag on the codec card |
Opening the file in metadata.video works even when nothing on your device can play it, because the readers parse the container and stream headers rather than decoding the picture. Only the Frames filmstrip needs a browser that can decode the codec.
Support depends on the operating system, the app and often the graphics hardware, so treat this as a starting point rather than a promise for any one model. VLC is left out because it plays all of these.
| Codec | iPhone and iPad | Android phones | Windows 10/11 built-in apps | Mac (QuickTime, Safari) | Chrome and Edge | Firefox | Smart TVs |
|---|---|---|---|---|---|---|---|
| H.264 (8-bit) | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| H.264 10-bit | Rarely | Rarely | Rarely | Rarely | Rarely | Rarely | Rarely |
| HEVC (H.265) | Yes | Most recent phones | With HEVC Video Extensions | Yes | Where the computer has a hardware decoder | On Windows with hardware decoding | Most 4K models |
| AV1 | Newer models only | Android 10+ (required from Android 14) | With AV1 Video Extension | Newer models only | Yes | Yes | Newer models |
| Apple ProRes | Yes | No | No | Yes | No | No | No |
| AAC audio | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| AC-3 / E-AC-3 (Dolby) audio | Yes | Depends on the maker | Varies | Yes | Rarely | Rarely | Usually |
| DTS audio | No | Rarely | Rarely | No | No | No | Varies by model and year |
Laptops can fall back to decoding in software when the graphics chip can’t help. TVs, streaming sticks and many phones rely entirely on a fixed hardware decoder, which accepts a specific list of codecs, profiles, levels and bit depths. A 4K HEVC Main 10 file at a high level, or an MKV with a DTS track, is a common mismatch. The profile and level on the codec checker tell you whether a file is near the top of what such devices handle.
Built-in players such as Windows Media Player, Photos, QuickTime and most Android galleries use the decoders the system provides. VLC carries its own, so it plays HEVC, AV1, ProRes, AC-3 and DTS on any platform. If you only need to watch the clip, this is the quickest fix and changes nothing about the file.
iPhones record HEVC by default. In Settings, Camera > Formats, Most Compatible switches new photos and videos to JPEG and H.264, and High Efficiency switches back. Apple notes that when you share by AirDrop, Messages or email, the iPhone may convert a video to H.264 automatically if the receiving device can’t use HEVC, and that importing to a computer can also convert unless you turn on Keep Originals under Settings > Apps > Photos. That is why the same clip can be HEVC on one machine and H.264 on another.
Recording 4K at high frame rates or in HDR produces files that older devices find hardest. If you mostly share to older PCs or TVs, lower resolution and frame rate settings help as much as the format choice. The HEVC vs H.264 guide covers the trade-off.
When the file has to play on a device you can’t change (a TV, a client’s laptop, an upload form), make a copy in MP4 with H.264 video and AAC audio. HandBrake is a free, open-source converter with ready-made presets for this; VLC’s Media > Convert/Save can do simple conversions; ffmpeg gives full control:
ffmpeg -i input.mkv -c:v libx264 -crf 20 -preset medium -pix_fmt yuv420p -c:a aac -b:a 192k output.mp4
If only the audio is the problem, convert just the sound and copy the picture untouched. This is faster and keeps the video quality exactly as it was:
ffmpeg -i input.mkv -c:v copy -c:a aac -b:a 192k output.mp4
Converting HDR footage to H.264 with the first command produces flat, washed-out colours, because the HDR picture needs tone mapping to become SDR. Check with the HDR video checker before converting, and keep the original either way.
Guessing at codecs wastes time: people install codec packs for a problem that is really a DTS soundtrack, or convert a whole film when copying the picture and converting the sound would have done. A two-minute look at the file avoids that.
For a deeper report with every stream and tag, use video file info; for command-line checks, the ffprobe guide shows the equivalent commands.
The player recognised the file but cannot decode the compressed picture inside it, usually because the format (often HEVC, AV1 or ProRes) or its profile is missing from the device. The file is normally intact and will play in a player that has the right decoder.
The audio stream uses a codec the device knows, such as AAC, while the video stream uses one it doesn’t. Installing the right decoder, using VLC or converting the video stream to H.264 fixes it.
The video codec is supported but the audio codec is not. Films and TV recordings often carry AC-3, E-AC-3 or DTS surround sound, which many phones and browsers can’t decode. Converting only the audio to AAC leaves the picture untouched.
Android’s standard format list doesn’t include Dolby or DTS audio, so support is up to each manufacturer and app. Try VLC for Android, or convert the soundtrack to AAC.
Computers can decode in software when the hardware can’t, while TVs depend on fixed hardware decoders with strict limits on codec, profile, level, bit depth and audio format. Check those values for the file, then compare them with the TV’s specifications.
The Microsoft Store listing for HEVC Video Extensions is paid (£0.79 in the UK at the time of writing), though some PCs ship with HEVC support already installed. The AV1 Video Extension is free.
No. It reads and explains the file, and can edit or remove metadata without re-encoding, but it does not convert codecs. Use VLC, HandBrake or ffmpeg for that.