Read the track picker before the waveform
PrivateMP3 lists audio tracks only; video and subtitle tracks are not offered as extraction choices. The picker appears when at least two audio tracks are found. It starts on the first audio track in the file. It does not automatically prefer your language or use Matroska's default or original-language flags. If the editor opens without a picker, PrivateMP3 found one audio track.
| Picker text | Meaning | Does not prove |
|---|---|---|
| 1., 2., 3.… | Track order in this file | Which track is the main audio |
| Language code | Language metadata in the file | That the tag is accurate |
| AAC, Opus, FLAC… | Codec inside the MKV | That it can be decoded here |
| mono, stereo, 6ch… | Reported channel count | Its purpose |
| no decoder | That track cannot be decoded here | That the MKV has no audio |
A missing language is shown as no language text at all. PrivateMP3 also hides the und code, which means the language was not identified. Codec and channel count remain useful when the language field is empty.
Language alone cannot identify commentary
The Matroska specification allows an audio track to carry a human-readable name, a language, and flags for commentary or content intended for people with visual impairments. This picker currently shows only the track order, language when available, codec, channel count and decoder status. It does not show the track name or those purpose flags. Two entries that both read English, AAC and stereo can still contain different programmes.
If the labels are identical, first open the local file in a player or media-information tool that exposes track names and purpose flags, then note the matching track position. The Play button on this page uses the browser's playback of the original MKV; it is not connected to the Audio track picker. The waveform is built from the selected track, but its shape cannot tell you which language or narration it contains. Neither is a reliable way to identify two otherwise identical tracks.
Choose the track before you edit
- Open the MKV and read every option in the Audio track picker.
- Select the intended track and wait for the Ready message. That selected track supplies the waveform and the converted output.
- Make cuts or volume changes only after the correct waveform has loaded.
- Choose MP3, M4A or WAV, then convert.
If you change tracks after selecting a range, cutting audio, changing volume or creating undo history, PrivateMP3 asks for confirmation. Continuing clears that work and scans the new track from the beginning; cancelling keeps the current track and edits. The page exports one selected audio track. It does not merge or mix several MKV tracks.
What “no decoder” changes
The no decoder label is specific to that audio track in the current browser. PrivateMP3 cannot draw its waveform or make a newly encoded MP3, WAV or M4A from that track, so Convert remains disabled. Another audio track in the same MKV may have a different codec and may work.
There is one narrow exception. If the selected track is AAC, the output is M4A, and the whole timeline is unchanged, PrivateMP3 can copy the compressed AAC packets into a new M4A container without decoding or re-encoding them. A cut or volume change removes that option. The page displays Copied without re-encoding — same audio, no quality loss.
when the copy route applies.
Pick an output for the selected track
- MP3 decodes the selected track and makes a new 192 kbps MP3. Use it when the destination specifically needs MP3.
- M4A keeps an eligible, unedited AAC track by packet copy. Other decodable tracks, or edited AAC, are encoded as new AAC.
- WAV expands the decoded audio into 16-bit PCM. It is useful as an editing file, but it cannot restore detail already lost in a compressed source.
When the intended track still will not load
This file has no audio track
means the container and its track list opened, but no track was classified as audio. A duration, waveform or decoder message occurs later, after an audio track was found. These are different failures. The waveform and Convert diagnostic guide follows the exact order used by PrivateMP3 and explains what to preserve or re-export at each stage.