Validate audio mix bitrate

app/operations/mix_audio.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import json
+import re
 from collections.abc import Sequence
 from pathlib import Path
 from typing import Any
@@ -45,6 +46,13 @@ def _track_params(params: dict[str, Any], count: int) -> list[dict[str, float]]:
     return tracks
 
 
+def _audio_bitrate(params: dict[str, Any]) -> str:
+    value = str(params.get("audio_bitrate", "192k")).strip().lower()
+    if not re.fullmatch(r"(?:32|48|64|96|128|160|192|224|256|320)k", value):
+        raise InputError("audio_bitrate must be a supported AAC bitrate")
+    return value
+
+
 async def add_audio(
     ffmpeg: FFmpegService,
     inputs: Sequence[InputMedia],
@@ -53,6 +61,7 @@ async def add_audio(
 ) -> OperationResult:
     require_inputs(inputs, 2)
     tracks = _track_params(params, len(inputs) - 1)
+    bitrate = _audio_bitrate(params)
     output = output_path(output_dir, "audio-mix", "mp4")
 
     filters: list[str] = []
@@ -85,7 +94,7 @@ async def add_audio(
             "-c:a",
             "aac",
             "-b:a",
-            str(params.get("audio_bitrate", "192k")),
+            bitrate,
             "-movflags",
             "+faststart",
             output,