如果 M4A 是丢失的, 和 AMR 是无损失的( 例如 MP3 {WAV), AMR 并不比 M4A 更好, 您无法收回已经丢弃的信息。 如果 M4A 是无损失的, AMR 是丢失的, AMR 代码压缩; 在 192 kbps, 多数内容的结果是透明的 。
Does the M4A to AMR converter keep ID3 / metadata tags?
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Yes — title, artist, album, year, track number, and album art are read from the M4A container and written into the AMR container where the format supports tags. All common targets (MP3, AAC, FLAC, OGG) handle tags fine; raw WAV does not.
我可以批量转换成 M4A 成百上千个文件 AMR 吗?
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Yes — drop a folder of M4A files in and we process them in parallel. Premium has more parallel workers and no per-file size cap, so a 500-file batch finishes in minutes rather than tens of minutes.
Will the AMR keep the same sample rate as M4A?
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默认是 。 - 48 kHz M4A 保留48 kHz在 AMR 中。 如果您需要降为兼容性样本( 96 kHz 44.1 kHz 用于 CD 燃烧), 样本率选项将在同一编码通行证中采用高质量的重新取样。
Yes — uploaded M4A files are processed in isolated workers and deleted within minutes. We never play back, store long-term, or share the audio content. The full retention window is in /privacy/.
转换一个 1小时 M4A 到 AMR 需要多久?
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Same-codec re-mux: 10 to 30 seconds. Re-encode to a different codec: typically 10 to 20% of source duration, so a 1-hour M4A → AMR finishes in 6 to 12 minutes. Batch jobs parallelize across workers for further speedups.
Why is the AMR louder or quieter than the M4A source?
If the M4A download is unprotected (no DRM), yes. DRM-encrypted streams (Spotify, Apple Music tracks) are encrypted at the bit level and we cannot process them. Bandcamp, SoundCloud downloads, personal recordings, and podcast files convert cleanly.
