HCOM to MP2 Converter

HCOM is a Huffman-coded audio format from the early Macintosh era, designed to shrink digitized sound for distribution on floppy disks and bulletin board systems when storage was precious and modems were slow. The encoder takes 8-bit unsigned PCM input, computes a frequency table of sample-delta values, and builds an optimal Huffman tree that replaces common deltas with short bit sequences. Compression ratios of 2:1 or better were typical for speech recordings, a meaningful saving when a 3.5-inch floppy held only 800 KB. Files were distributed as Macintosh resource forks and played through utilities like SoundApp and the BinHex ecosystem that defined Mac software exchange in the late 1980s. The format supported sample rates up to 22.255 kHz, matching the output capabilities of original Macintosh sound hardware. Tools such as SoX retain HCOM decoding support, ensuring that archived recordings remain accessible decades later. HCOM holds three practical advantages for preservation work: lossless compression that recovers the original samples exactly, a self-contained Huffman table embedded in each file for dependency-free decoding, and historical prevalence across thousands of vintage Mac sound archives.

MP2 (MPEG-1 Audio Layer II), also known by its original project name MUSICAM, is a perceptual audio codec standardized as part of ISO/IEC 11172-3 in 1993. While its successor MP3 captured the consumer spotlight, MP2 carved out a durable niche in professional broadcasting that it holds to this day. The codec splits audio into 32 sub-bands via a polyphase filter bank, applies a psychoacoustic model to determine masking thresholds, then quantizes and Huffman-codes each sub-band accordingly. Typical broadcast deployments use 192-384 kbps for stereo, yielding transparent quality with lower encoder complexity and better error resilience than Layer III. These properties explain why DVB television, DAB digital radio, and the HDV camcorder standard all mandate or prefer MP2. Encoder latency is shorter too, an important trait for live broadcasting where lip-sync matters. Three advantages keep MP2 relevant decades after standardization: graceful degradation under transmission errors vital for over-the-air signals, minimal encoding delay that suits real-time broadcast chains, and entrenched regulatory acceptance across European and Asian broadcast frameworks.