- **ld-chroma-decoder** - Color decoder for TBC LaserDisc video to RGB conversion

- **ld-export-metadata** - Export TBC metadata to human-readable formats

- **ld-json-converter** - Convert between metadata formats

**⚠️ DEPRECATED: This single tool has been deprecated and replaced by a suite of specialized tools in `tools/efm-decoder/`. Use `efm-decoder-audio` for standard audio decoding, or other efm-decoder tools for specific use cases.**

**Eight-to-Fourteen Modulation (EFM) Digital Audio Decoder**

**Note:** This tool is deprecated. Please use the efm-decoder suite of tools located in `tools/efm-decoder/` for EFM decoding. The functionality of this single tool has been split into multiple specialized tools for better flexibility and control.

ld-process-efm decodes digital audio data from LaserDisc captures. It processes Eight-to-Fourteen Modulation (EFM) encoded PCM audio data embedded in the RF signal, producing raw audio streams or WAV files.

- **Full EFM Decoder**: Complete digital audio extraction

- **Error Correction**: Reed-Solomon error correction (CIRC)

- **Sync Detection**: Robust frame synchronization

- **Parity Checking**: Data integrity validation

- **Sample Rates**: 44.1 kHz (CD quality)

- **Bit Depth**: 16-bit linear PCM

- **Channels**: Stereo (2 channel)

- **Byte Order**: Configurable endianness

- **Error Concealment**: Interpolation of uncorrectable errors

- **Dropout Handling**: Graceful degradation on signal loss

- **Statistics Reporting**: Detailed error and quality metrics

- **Validation**: Audio stream integrity checking

- **Raw PCM**: Uncompressed audio stream

- **WAV**: Standard WAV file format

- **Metadata**: Error statistics and quality reports

ld-process-efm [options] <input.efm> [output.pcm]

Or when integrated with ld-decode:

ld-decode --digital-efm input.ldf output.tbc output.efm

ld-process-efm output.efm output.pcm

- `-h, --help`: Display help on command-line options

- `-v, --version`: Display version information

- `-d, --debug`: Show debug information

- `-q, --quiet`: Suppress info and warning messages

- `-c, --conceal`: Conceal corrupt audio data (default)

- `-s, --silence`: Silence corrupt audio data

- `-g, --pass-through`: Pass-through corrupt audio data

- `-p, --pad`: Pad start of audio from 00:00 to match initial disc time

- `-b, --data`: Decode F1 frames as data instead of audio

- `-D, --dts`: Audio is DTS rather than PCM (allow non-standard F3 syncs)

- `-t, --time`: Non-standard audio decode (no time-stamp information)

- `--debug-efmtof3frames`: Show EFM To F3 frame decode detailed debug

- `--debug-syncf3frames`: Show F3 frame synchronisation detailed debug

- `--debug-f3tof2frames`: Show F3 To F2 frame decode detailed debug

- `--debug-f2tof1frame`: Show F2 to F1 frame detailed debug

- `input`: Input EFM file (required)

- `output`: Output audio file (required)

- `-q, --quiet`: Suppress info and warning messages

- `-d, --debug`: Show debug

ld-process-efm input.efm output.pcm

ld-process-efm -s input.efm output.pcm

ld-process-efm -p input.efm output.pcm

ld-process-efm -b input.efm output.dat

ld-process-efm -D input.efm output.pcm

ld-decode --digital-efm disc.ldf video.tbc audio.efm

ld-process-efm --audio-format wav audio.efm audio.wav

- **Encoding**: 8 data bits → 14 channel bits

- **Purpose**: DC-free signal, clock recovery

- **Frame Structure**: 588 channel bits per audio frame

- **Sync Patterns**: 24-bit + 3 merge bits

- **Method**: Cross-Interleaved Reed-Solomon Code

- **C1 Decoder**: First-level error correction (4 bytes)

- **C2 Decoder**: Second-level error correction (4 bytes)

- **Interleaving**: Delay-based (108 frames)

- **Capability**: Corrects bursts up to ~3900 bits

- **Sample Rate**: 44,056 Hz or 44,100 Hz (depends on disc)

- **Quantization**: 16-bit linear PCM

- **Channels**: 2 (Left and Right interleaved)

- **Frame Rate**: 7,350 frames/second

When using `--statistics`, ld-process-efm reports:

- **<0.01% errors**: Excellent quality

- **0.01-0.1% errors**: Good quality, minor issues

- **0.1-1% errors**: Audible artifacts, poor source

- **>1% errors**: Severe problems, check RF capture

1. **Interpolation**: Linearly interpolate between good samples

2. **Previous Sample Hold**: Repeat last good sample

3. **Muting**: Output silence (if concealment disabled)

- Applied to uncorrectable errors after CIRC decoding

- Conceals up to ~13ms of audio (typical)

- Longer errors result in audible glitches

ld-process-efm --audio-format wav input.efm raw.wav

flac --best raw.wav -o output.flac

lame -V 0 raw.wav output.mp3

ld-decode --digital-efm side1.ldf side1.tbc side1.efm

ld-process-efm --audio-format wav side1.efm side1.wav

ld-decode --digital-efm side2.ldf side2.tbc side2.efm

ld-process-efm --audio-format wav side2.efm side2.wav

sox side1.wav side2.wav complete.wav

ld-process-efm --statistics --output-metadata meta.sqlite input.efm output.wav

ld-export-metadata --csv meta.sqlite

**No audio output:**

- Verify EFM file is not empty (`ls -lh input.efm`)

- Check that ld-decode used `--digital-efm` option

- Ensure disc has digital audio tracks (not all LaserDiscs do)

**High error rates:**

- Improve RF signal quality (better connection, cleaning)

- Check for disc damage (scratches, rot)

- Verify proper tracking during capture

- Try recapturing with different settings

**Sync errors:**

- May indicate wrong sample rate or corrupted EFM file

- Check ld-decode didn't report errors during capture

- Verify file is complete (not truncated)

**Audible glitches:**

- Normal for damaged discs (physical media errors)

- Consider error concealment if disabled

- May need manual audio repair in editing software

**Wrong sample rate:**

- Some discs use 44,056 Hz instead of 44,100 Hz

- Use `--sample-rate` to override if needed

- Check disc specifications

- **PCM Audio**: Highest quality, occupies video lines

- **AC-3 (Dolby Digital)**: Compressed surround (use ld-process-ac3)

- **Analog Audio**: Standard LaserDisc audio (decoded separately)

- Not all LaserDiscs have digital audio

- Common on later discs (1990s+)

- Music discs typically have PCM

- Movies may have AC-3 instead

- **SMPTE Time Code**: SMPTE format time codes