Testing methodology
Reproducible results, not borrowed claims.
We test the processing path, verify the output with FFprobe, and publish measured examples generated from controlled synthetic audio. Private customer uploads are never reused as test material.
Fixtures
Pink-noise and sine components produce repeatable, non-private 44.1 kHz references in WAV, MP3, M4A, and MP4 containers.
Production engine
The live worker runs FFmpeg 5.1.9. Reference fixtures and the August 2026 benchmark pass were verified with FFmpeg 8.1.2.
Validation
FFprobe confirms duration, codec, sample rate, channels, bitrate, and readability after processing. End-to-end jobs also verify downloads.
Eight measured processing checks
Audio Compressor
- Source fixture
- 60-second, 44.1 kHz stereo WAV synthetic reference — 10.58 MB
- Processing settings
- Balanced preset, MP3 at 160 kbps stereo
- Measured output
- 1.20 MB
- What the result shows
- An 88.7% size reduction. Real results vary with duration, codec, channel layout, and encoding mode.
Compress Audio to Target Size
- Source fixture
- 180-second, 44.1 kHz stereo WAV synthetic reference — 31.75 MB
- Processing settings
- 5 MB target, calculated 228 kbps MP3 (mapped to an encoder-supported rate)
- Measured output
- 5.04 MB decimal / 4.81 MiB
- What the result shows
- The result stayed below the tool's 5 MiB byte budget; container overhead and supported-rate rounding explain the difference.
MP3 Compressor
- Source fixture
- 60-second MP3 at 320 kbps — 2.40 MB
- Processing settings
- Speech-oriented MP3 at 96 kbps
- Measured output
- 0.72 MB
- What the result shows
- A 70.0% reduction, closely matching the bitrate ratio for this constant-bitrate test.
M4A to MP3 Converter
- Source fixture
- 60-second AAC-in-M4A reference at 128 kbps — 0.97 MB
- Processing settings
- Standard MP3 at 192 kbps stereo
- Measured output
- 1.44 MB
- What the result shows
- The MP3 is larger because the selected MP3 bitrate is higher; conversion improves compatibility, not fidelity.
WAV to MP3 Converter
- Source fixture
- 60-second, 16-bit, 44.1 kHz stereo PCM WAV — 10.58 MB
- Processing settings
- Standard MP3 at 192 kbps stereo
- Measured output
- 1.44 MB
- What the result shows
- An 86.4% size reduction while retaining a high-quality listening copy.
Audio Trimmer
- Source fixture
- 60-second MP3 at 320 kbps — 2.40 MB
- Processing settings
- Keep 00:10–00:25 with MP3 stream copy
- Measured output
- 0.60 MB for 15 seconds
- What the result shows
- The output is approximately one quarter of the source because one quarter of the duration was retained without re-encoding.
MP4 to MP3 Converter
- Source fixture
- 30-second 640×360 MP4 with 128 kbps AAC audio — 0.51 MB
- Processing settings
- Extract and encode MP3 at 192 kbps
- Measured output
- 0.72 MB
- What the result shows
- The audio-only MP3 is larger in this synthetic case because its bitrate exceeds the source AAC track and the test video is intentionally simple.
Audio Format Converter
- Source fixture
- 60-second, 16-bit, 44.1 kHz stereo WAV — 10.58 MB
- Processing settings
- Convert to Opus at 128 kbps
- Measured output
- 0.69 MB
- What the result shows
- A 93.5% size reduction on the synthetic reference; this is a lossy delivery copy, not a lossless replacement for the WAV.
What the numbers do—and do not—prove
Synthetic references make settings reproducible, but they do not predict perceived quality for every voice, instrument, or recording. Codec behavior changes with spectral complexity, transients, channel relationships, source artifacts, and encoder version.
We publish sizes to explain duration and bitrate, not to promise every input will produce the same byte count. Target-size results include container overhead and bitrate rounding, so strict upload workflows should keep a safety margin. MB means 1,000,000 bytes; MiB means 1,048,576 bytes.
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