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ld process efm
Format | Info | Sample Rate | Bit-Depth | Extention |
---|---|---|---|---|
Analog Track | Stereo or Mono | 44.1KHz | 16-bit | .pcm |
Dolby AC-3 | Stereo PCM | 44.1KHz | 16-bit | .ac3 |
Dolby DTS | Surround 5.1 | 44.1KHz | 16/24-bit | .dts |
This application processes the raw digital .efm
output from ld-decode into either digital audio or data.
ld-process-efm implements both audio and data error detection and correction.
Requires --AC3
flag in ld-decode to enable extraction of signal data.
This can be 2.0 Stereo or 4.0, 5.1 Surround
5.1 Surround
![](assets/graphics/ac3_5.1_surround.png)
4.0 Surround
![](assets/graphics/surround_4.1.png)
AC-3 discs take the Right channel analog track area, so Left channel may contain an mono analog audio track.
LaserDisc digital audio is based on the standards used for CDs (stereo 44.1KHz 16-bit PCM), which require the digital audio stream to contain periodic timestamps so the player can tell where it is on the disc.
Since LaserDisc players get this information from the video instead, quite a lot of LaserDiscs don't bother to include audio timestamps.
You can tell if you're decoding a disc like this by looking at the statistics printed by ld-process-efm: if no data is coming out of the F3 frame synchronisation
phase, try using the --time
option to not require timestamps. (The downside of this is that it makes error padding less effective, so only use it if you need to.)
![](assets/graphics/dts_5.1.png)
If you have a DTS disc, use the --dts
option: this disables audio error concealment, and makes ld-process-efm accept a variation of the CD audio standard (a different F3 Sync 0 sequence) used by some DTS discs. Many DTS discs need --time
too.
The output will be a .dts
file.
The channel map is as follows for surround 5.1
- Left Front
- Right Front
- Center Channel
- Left Rear
- Right Rear
- LFE (Subwoofer)
Note: you can convert the .pcm
analog audio to standard .wav
with:
ffmpeg -f s16le -ar 44.1k -ac 2 -i input.pcm output_file.wav
Syntax:
ld-process-efm <options> <input EFM file name> <output data file name>
Options:
-h, --help Displays help on commandline options.
--help-all Displays help including Qt specific options.
-v, --version Displays version information.
-d, --debug Show debug
-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
--debug-f1toaudio Show F1 to audio detailed debug
--debug-f1todata Show F1 to data detailed debug
Arguments:
input Specify input EFM file
output Specify output file
CLI options:
-
Audio
- Conceal corrupt audio data - Attempts to conceal corrupt audio data using the concealment type selected in the following section
- Silence corrupt audio data - Silences any corrupt samples
- Pass-through corrupt audio data - Passes any corrupt samples through to the output as-is
-
Concealment type
- Linear interpolation - Interpolates between last-good and next-good samples to conceal errors
-
Options
- Pad start of audio from 00:00 to match initial disc time - Pads the start of the input sample to ensure the output starts from the 00:00 time of the disc. Useful for assembling partial captures.
- Decode F1 frames as audio - Decode F1 frames as audio data
- Decode F1 frames as data - Decode F1 frames as data
- Non-standard audio decode (no time-stamp information in input EFM)
-
Detailed debugging for development
- EFM to F3 Frame debug
- F3 and section debug
- F3 to F2 Frame decoding debug
- F2 to F1 Frame decoding debug
- F1 Frame to audio samples debug
- F1 Frame to data sector debug
- Basic usage
- TBC Video Export
- PAL decode guide
- NTSC decode guide
- Working with multiple discs
- Working with subtitles
- Disc images to download
- ld-decode
- ld-analyse
- ld-chroma-decoder
- ld-process-vbi
- ld-export-metadata
- ld-dropout-correct
- ld-process-efm
- ld-discmap
- ld-disc-stacker
- ld-process-vits
- ld-lds-converter
- ld-chroma-encoder