Why Extracting Audio to M4A Is Instant (and WAV Isn't)
Extract audio from a video to M4A and it's done almost instantly, regardless of how long the video is. Pick WAV instead and suddenly there's real processing time involved. That asymmetry isn't a quirk — it comes down to what the two output formats actually require the tool to do, and understanding it also explains why WAV or FLAC output doesn't give you "better" audio than M4A did.
Why M4A/AAC extraction is nearly instant
Most video files already carry their audio track encoded as AAC — that's the standard audio codec inside an MP4 container, and it's common across MOV, MKV, and most other video formats too. When the requested output is M4A or AAC, the existing audio stream can simply be copied out of the video container and placed into an audio-only one, with no decoding or re-encoding involved at all. This is sometimes called a "stream copy" or "remux" — moving data between containers rather than transforming it. Since nothing about the audio itself is being processed, the operation finishes in about a second regardless of whether the source video is one minute or sixty.
Why other formats take real processing time
Requesting MP3, WAV, FLAC, OGG, or AIFF output means the original AAC audio has to be fully decoded back into raw audio samples, and then encoded again into the new target format. Both steps take real computation, and that computation scales with how long the video actually is — a 45-minute video takes proportionally longer to decode and re-encode than a 3-minute one, unlike the stream-copy path, which barely notices the difference.
Why WAV or FLAC doesn't restore lost quality
It's a reasonable assumption that a lossless format like WAV or FLAC should sound better than AAC — lossless formats generally do preserve more detail than lossy ones. But that assumption only holds when the lossless format is wrapping audio that was never compressed in the first place. If the video's original audio track was already AAC — which is the common case — that compression already happened, and it already discarded whatever detail AAC's encoding process discards. Converting that AAC audio into WAV or FLAC afterward doesn't undo any of that; it just repackages the identical, already-lossy audio data into a much larger file. You end up with more megabytes, not more fidelity.
When lossless output actually helps
The exception is when the source video's audio track was itself uncompressed or losslessly encoded to begin with — something that shows up occasionally in professional camera footage or certain production workflows, though it's uncommon in typical phone videos, screen recordings, or downloaded clips. In that specific case, extracting to WAV or FLAC genuinely preserves everything the source had, where extracting to a lossy format like MP3 would introduce compression that wasn't there before. For the much more common case of AAC-encoded video audio, M4A or AAC output gives you the same audio quality as WAV or FLAC would, just faster and in a smaller file.
Picking the right output for your use case
If you're just pulling audio for transcription, editing reference, or general listening, M4A or AAC is the faster choice with no real downside for typical video sources. If you're archiving audio for long-term storage or feeding it into a workflow that specifically requires WAV or FLAC, those formats work fine too — you're just not gaining fidelity over M4A in the process, only compatibility with whatever expects an uncompressed file.
Our Video to Audio Converter runs this exact process — upload MP4, MOV, MKV, or another supported video format, choose your output, and download the audio, no account or software install needed.