fix(video): take the audio rate from the loaded vocoder

Pipelines rarely report a sample rate, so the save path fell back to 24000.
LTX-2.3 and 2.5 run at 48k, and muxing at half the rate drops the track an
octave. The rate now comes from the vocoder, as the LTX tab already did.

modules/video_models/video_run.py

@@ -326,7 +326,7 @@ def run(selected: models_def.Model, *,
         p=p,
         pixels=pixels,
         audio=waveform,
-        aac_sample_rate=getattr(p, 'audio_sampling_rate', None) or 24000,
+        aac_sample_rate=video_save.get_audio_rate(p),
         binary=processed.bytes,
         mp4_fps=save_fps,
         mp4_codec=mp4_codec,

modules/video_models/video_save.py

@@ -11,6 +11,16 @@ from modules.logger import log
 from modules.video_models.video_utils import check_av
 
 
+def get_audio_rate(p=None, default: int = 24000) -> int:
+    # pipeline output wins when it reports a rate, else the loaded vocoder: LTX-2.0 runs at 24k,
+    # 2.3 and 2.5 at 48k, and muxing at the wrong rate shifts the pitch
+    rate = getattr(p, 'audio_sampling_rate', None) if p is not None else None
+    if not rate:
+        vocoder = getattr(shared.sd_model, 'vocoder', None)
+        rate = getattr(getattr(vocoder, 'config', None), 'output_sampling_rate', None)
+    return int(rate) if rate else default
+
+
 def get_video_filename(p:processing.StableDiffusionProcessingVideo):
     from modules.image.namegen import FilenameGenerator
     from modules.paths import resolve_output_path