Multiple Logical Files

A single .dlis physical file can contain more than one logical file. Each logical file is a self-contained recording unit with its own ORIGIN, set of channels, frames, and parameters.

This is common in:

Multi-pass acquisitions where each pass is a separate logical file
Files that combine real-time and memory recordings
Composite files built by merging several runs

Detecting multiple logical files

const dlis = await DLISFile.fromFile('multi.dlis');

console.log('Logical files:', dlis.logicalFiles.length);

for (const [i, lf] of dlis.logicalFiles.entries()) {
  console.log(`\nLogical file ${i + 1}: id="${lf.id}"`);
  console.log('  Channels:', lf.channels.size);
  console.log('  Frames  :', lf.frames.size);
  console.log('  Well    :', lf.origin?.wellName ?? '(none)');
}

Iterating all frames across all logical files

for (const lf of dlis.logicalFiles) {
  for (const frame of lf.frames.values()) {
    const result = frame.decode();
    if (!result) continue;
    console.log(
      `LF "${lf.id}"  frame "${frame.name}"`,
      result.frameCount, 'rows,',
      frame.channelNames.join(', ')
    );
  }
}

Shortcut properties

DLISFile.origin, DLISFile.channels, and DLISFile.frames are shortcuts to logicalFiles[0]. For files with only one logical file this is always correct. For multi-logical-file cases you should iterate logicalFiles explicitly.

Same channel name in different logical files

Each logical file has its own channel registry. A channel named GR in logical file 0 and a GR in logical file 1 are separate objects and may have different OBNAMEs, repcodes, or units.

const gr0 = dlis.logicalFiles[0].getChannel('GR');
const gr1 = dlis.logicalFiles[1].getChannel('GR');

console.log(gr0?.obname);  // { origin: 1, copy: 0, name: 'GR' }
console.log(gr1?.obname);  // { origin: 2, copy: 0, name: 'GR' }