Allow import/export completely custom SEG-Y via spec override environ…

…ment variable (#440)

* Add environment variable for SEG-Y text header encoding (#439)

* Update segy dependency to version 0.2.2

Upgraded segy from version 0.2.0 to 0.2.2 in pyproject.toml.

* allow full spec override via json env var.

pyproject.toml

@@ -31,7 +31,7 @@ dask = ">=2024.6.1"
 tqdm = "^4.66.4"
 psutil = "^6.0.0"
 fsspec = ">=2024.9.0"
-segy = "^0.2.0"
+segy = "^0.2.2"
 rich = "^13.7.1"
 urllib3 = "^1.26.18" # Workaround for poetry-plugin-export/issues/183
 

src/mdio/segy/compat.py

@@ -8,6 +8,7 @@
 
 from __future__ import annotations
 
+import os
 from importlib import metadata
 
 from segy.alias.segyio import SEGYIO_BIN_FIELD_MAP
@@ -57,14 +58,19 @@ def get_trace_fields(version: str) -> list[HeaderField]:
 
 def mdio_segy_spec(version: str | None = None) -> SegySpec:
     """Get a SEG-Y encoding spec for MDIO based on version."""
+    spec_override = os.getenv("MDIO__SEGY__SPEC")
+
+    if spec_override is not None:
+        return SegySpec.model_validate_json(spec_override)
+
     version = MDIO_VERSION if version is None else version
 
     binary_fields = get_binary_fields()
     trace_fields = get_trace_fields(version)
 
     return SegySpec(
         segy_standard=None,
-        text_header=TextHeaderSpec(),  # default EBCDIC
+        text_header=TextHeaderSpec(),
         binary_header=HeaderSpec(fields=binary_fields, item_size=400, offset=3200),
         trace=TraceSpec(
             header=HeaderSpec(fields=trace_fields, item_size=240),