Raw PCM与FFmpeg解码MP3哪个更快？Android音频卡顿问题咨询

Hey Matt, let's break down your questions step by step since I've dealt with similar audio playback bottlenecks on Android before.

Your intuition about the Player class reloading audio data on every callback is spot-on—this is almost certainly the root cause of your stuttering with 1000ms clips. Audio callback threads have extremely tight latency requirements (they need to finish their work in just a few milliseconds to avoid glitches). When you load a full 1000ms Raw PCM file from disk every single callback, the disk I/O and memory copy overhead is drastically larger than with a 160ms file. It's not the file size itself that's the problem—it's the repeated blocking I/O operation hogging the audio thread.

Let's compare the two formats based on real-world use cases:

• Preloaded Raw PCM: This is the fastest possible playback scenario. Raw files are uncompressed, so there's no decoding overhead—you just feed the preloaded byte array directly to the audio output. If you load your 1000ms Raw file once during initialization (instead of on every callback), you'll eliminate the stutter entirely, and performance will beat any compressed format.
• FFmpeg-Decoded MP3: MP3 requires CPU (or hardware) decoding to convert it to PCM first. The decoding step adds some overhead, but if you decode the entire MP3 in a background thread upfront and cache the PCM data in memory, the playback performance will be nearly identical to preloaded Raw. MP3's main advantage is smaller APK size (it's roughly 1/10 the size of equivalent Raw PCM), not raw playback speed.
• On-the-fly loading/decode: If you stick to loading Raw on every callback, the 1000ms file will keep stuttering due to disk I/O. For MP3, on-the-fly decoding per callback would also cause stutter, but might be slightly better than large Raw files since MP3s are smaller and faster to read from disk.

I haven't seen formal public benchmarks comparing Raw vs MP3 specifically for Android audio callback scenarios, but from hands-on work:

• When both formats are preloaded into memory, Raw has a tiny performance edge (no decoding step), but it's negligible for end users.
• When loading directly from disk, MP3 often outperforms large Raw files because the smaller file size reduces disk I/O time, which is a bigger bottleneck than MP3 decoding overhead.

1. Fix the Player class first: Modify your rendering logic to load the Raw audio data once during initialization (store it in a global byte array), then use that in-memory data for every callback. This should immediately resolve the stuttering with long clips.
2. Use Systrace to confirm: Generate a Systrace during playback to check the audio thread (usually labeled with AudioTrack). Look for disk I/O latency spikes—this will confirm that repeated file loading is the culprit.
3. MP3 as a secondary option: If APK size is a concern, convert your files to MP3 and use FFmpeg or MediaCodec to decode them in a background thread upfront. Cache the decoded PCM in memory, and you'll get the best of both worlds: smaller APK size and smooth playback.

内容的提问来源于stack exchange，提问作者Matt Strom