Upload your MP4 video. PDF.to pulls the audio track out, encodes it to M4R, and gives you a M4R-only download. The video stream is discarded.
Will the audio in the M4R match the original MP4 quality?
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If the source audio is already in a codec compatible with M4R, we stream-copy without re-encoding — bit-identical to the original. Otherwise we re-encode at 192 kbps by default for near-transparent quality.
Yes, within the free size limit. PRO supports much larger MP4 files and parallel batch extraction.
Does PDF.to read or store my MP4 content?
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No. The MP4 video and the M4R audio output are deleted within an hour. Conversion runs in an isolated worker.
Can I batch-extract audio from multiple MP4 files?
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Yes — drop a folder of MP4 videos and you will get a ZIP of M4R files back, one per source video.
Will the M4R preserve tags and metadata?
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Title, artist, and album tags are populated from the MP4 container metadata when available. You can edit them after extraction with our audio-tag tool.
変換はストリーミングビデオ URL で動作しますか？
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No — PDF.to converts files you upload, not third-party stream URLs. Download the MP4 legally first, then upload it for M4R extraction.
Why is the M4R file much smaller than the MP4 video?
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Because the video stream (typically 90%+ of file size) is discarded. Only the audio track ends up in the M4R, which is why it can drop from gigabytes to a few megabytes.
