---
name: "vcd2lxt"
section: "1"
platform: "linux"
package: "gtkwave"
version: "3.3.128-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/vcd2lxt"
---

# vcd2lxt(1)

Converts VCD files to interlaced or linear LXT files

## NAME

vcd2lxt - Converts VCD files to interlaced or linear LXT files

## SYNTAX

vcd2lxt \[*VCDFILE*\] \[*LXTFILE*\] \[*option*\]...

## DESCRIPTION

Converts VCD files to interlaced or linear LXT files.  Noncompressed interlaced files will provide the fastest access, linear files will provide the slowest yet have the greatest compression ratios.

## OPTIONS

- **-stats**

  Prints out statistics on all nets in VCD file in addition to performing the conversion.

- **-clockpack**

  Apply two-way subtraction algorithm in order to identify nets whose value changes by a constant XOR or whose value increases/decreases by a constant amount per constant unit of time.  This option can reduce dumpfile size dramatically as value changes can be represented by an equation rather than explicitly as a triple of time, net, and value.

- **-chgpack**

  Emit data to file after being filtered through zlib (gzip).

- **-linear**

  Write out LXT in "linear" format with no backpointers.  These are re-generated during initialization in *gtkwave*.  Additionally, use libbz2 (bzip2) as the compression filter.

- **-dictpack** \<*size*\>

  Store value changes greater than or equal to *size* bits as an index into a dictionary.  Experimentation shows that a value of 18 is optimal for most cases.

## EXAMPLES

Note that you should specify dumpfile.vcd directly or use "-" for stdin.

- vcd2lxt dumpfile.vcd dumpfile.lxt -clockpack -chgpack -dictpack 18

  This turns on clock packing, zlib compression, and enables the dictionary encoding.  Note that using no options writes out a normal LXT file.

- vcd2lxt dumpfile.vcd dumpfile.lxt -clockpack -linear -dictpack 18

  Uses linear mode for even smaller files.

## AUTHORS

Anthony Bybell \<bybell@rocketmail.com\>

## SEE ALSO

[*lxt2vcd*(1)](/lxt2vcd/1.md) [*vcd2lxt2*(1)](/vcd2lxt2/1.md) [*gtkwave*(1)](/gtkwave/1.md)