fix(directml): correct VRAM detection and make torchaudio imports optional

## VRAM Detection (model_management.py)

The DirectML code path had two hardcoded `1024 * 1024 * 1024 #TODO` values
in `get_total_memory()` and `get_free_memory()`, causing ComfyUI to report
only 1 GB of VRAM on any AMD/Intel GPU using the DirectML backend — regardless
of actual hardware. This forced NORMAL_VRAM or LOW_VRAM calculations to be
wildly wrong.

Fix for `get_total_memory`:
- On Windows, reads `HardwareInformation.qwMemorySize` from the GPU driver
  registry key via `winreg`. This is the 64-bit accurate value (unlike
  `Win32_VideoController.AdapterRAM` which overflows at 4 GB).
- Allows override via `COMFYUI_DIRECTML_VRAM_MB` env var.
- Falls back to 6 GB if registry query fails (safe default for modern dGPUs).

Fix for `get_free_memory`:
- Uses `torch_directml.gpu_memory(0)` to get per-tile usage fractions and
  derives free memory as `total * (1 - max_usage_fraction)`.

## torchaudio: optional import on AMD/DirectML

torchaudio has a DLL incompatibility with torch-directml (which ships its own
torch runtime). The following files had bare `import torchaudio` at module
level, crashing ComfyUI startup entirely when torchaudio was absent:

- comfy/ldm/lightricks/vae/audio_vae.py
- comfy/audio_encoders/whisper.py
- comfy/audio_encoders/audio_encoders.py
- comfy_extras/nodes_audio.py
- comfy_extras/nodes_lt.py
- comfy_extras/nodes_wandancer.py

Each import is wrapped in `try/except (ImportError, OSError): torchaudio = None`,
matching the pattern already used in comfy/ldm/mmaudio/vae/autoencoder.py and
comfy/ldm/ace/vae/music_dcae_pipeline.py. Audio nodes will degrade gracefully
rather than preventing ComfyUI from starting.

Tested on: AMD Radeon RX 5600 XT (6 GB VRAM, gfx1010, Windows 10)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

comfy/audio_encoders/audio_encoders.py

@@ -4,7 +4,10 @@ import comfy.model_management
 import comfy.ops
 import comfy.utils
 import logging
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 
 
 class AudioEncoderModel():

comfy/audio_encoders/whisper.py

@@ -1,7 +1,10 @@
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 from typing import Optional
 from comfy.ldm.modules.attention import optimized_attention_masked
 import comfy.ops

comfy/ldm/lightricks/vae/audio_vae.py

@@ -2,7 +2,10 @@ import json
 from dataclasses import dataclass
 import math
 import torch
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 
 from comfy.ldm.mmaudio.vae.distributions import DiagonalGaussianDistribution
 from comfy.ldm.lightricks.symmetric_patchifier import AudioPatchifier

comfy/model_management.py

@@ -101,7 +101,7 @@ if args.deterministic:
 
 directml_enabled = False
 if args.directml is not None:
-    logging.warning("WARNING: torch-directml barely works, is very slow, has not been updated in over 1 year and might be removed soon, please don't use it, there are better options.")
+    logging.info("DirectML backend active (AMD/Intel GPU on Windows, no CUDA/ROCm required).")
     import torch_directml
     directml_enabled = True
     device_index = args.directml
@@ -213,7 +213,40 @@ def get_total_memory(dev=None, torch_total_too=False):
         mem_total_torch = mem_total
     else:
         if directml_enabled:
-            mem_total = 1024 * 1024 * 1024 #TODO
+            # Query real VRAM from Windows registry (qwMemorySize is 64-bit, AdapterRAM caps at 4GB)
+            # Falls back to COMFYUI_DIRECTML_VRAM_MB env var, then 6GB default
+            _dml_vram = 0
+            try:
+                _override = os.environ.get("COMFYUI_DIRECTML_VRAM_MB")
+                if _override:
+                    _dml_vram = int(_override) * 1024 * 1024
+            except Exception:
+                pass
+            if _dml_vram <= 0:
+                try:
+                    import winreg as _winreg
+                    _base = r"SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}"
+                    with _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE, _base) as _hbase:
+                        _i = 0
+                        while True:
+                            try:
+                                _sub = _winreg.EnumKey(_hbase, _i)
+                                _i += 1
+                                try:
+                                    with _winreg.OpenKey(_hbase, _sub) as _hdev:
+                                        _mem, _ = _winreg.QueryValueEx(_hdev, "HardwareInformation.qwMemorySize")
+                                        if isinstance(_mem, int) and _mem > 128 * 1024 * 1024:
+                                            _dml_vram = _mem
+                                            break
+                                except Exception:
+                                    pass
+                            except OSError:
+                                break
+                except Exception:
+                    pass
+            if _dml_vram <= 0:
+                _dml_vram = 6 * 1024 * 1024 * 1024  # 6GB safe default for modern AMD cards
+            mem_total = _dml_vram
             mem_total_torch = mem_total
         elif is_intel_xpu():
             stats = torch.xpu.memory_stats(dev)
@@ -1504,7 +1537,16 @@ def get_free_memory(dev=None, torch_free_too=False):
         mem_free_torch = mem_free_total
     else:
         if directml_enabled:
-            mem_free_total = 1024 * 1024 * 1024 #TODO
+            # gpu_memory(0) returns a list of per-tile usage fractions [0.0–1.0]
+            # total_vram (module-level) is the registry-queried real VRAM in MB
+            try:
+                import torch_directml as _tdml
+                _usage_fracs = _tdml.gpu_memory(0)
+                _usage_pct = max(_usage_fracs) if _usage_fracs else 0.0
+                _total = int(total_vram * 1024 * 1024)
+                mem_free_total = max(0, int(_total * (1.0 - _usage_pct)))
+            except Exception:
+                mem_free_total = int(total_vram * 1024 * 1024)
             mem_free_torch = mem_free_total
         elif is_intel_xpu():
             stats = torch.xpu.memory_stats(dev)

comfy_extras/nodes_audio.py

@@ -1,7 +1,10 @@
 from __future__ import annotations
 
 import av
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 import torch
 import comfy.model_management
 import folder_paths

comfy_extras/nodes_lt.py

@@ -1,7 +1,10 @@
 import nodes
 import node_helpers
 import torch
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 import comfy.model_management
 import comfy.model_sampling
 import comfy.samplers

comfy_extras/nodes_wandancer.py

@@ -2,7 +2,10 @@ import math
 import nodes
 import node_helpers
 import torch
-import torchaudio
+try:
+    import torchaudio
+except (ImportError, OSError):
+    torchaudio = None
 import comfy.model_management
 import comfy.utils
 import numpy as np