Update MP4 format string for iOS compatibility

iOS has strict requirements for video files, requiring h264 or h265 video codec and aac audio codec in MP4 container. This update to the MP4 format string tries to get a fully compatible file first, followed by the right video codec and any M4A audio (audio is much faster to convert if needed), and then falls back to the original behaviour of getting the best available MP4 video and M4A audio.

app/dl_formats.py

@@ -2,6 +2,7 @@ import copy
 
 AUDIO_FORMATS = ("m4a", "mp3", "opus", "wav")
 
+
 def get_format(format: str, quality: str) -> str:
     """
     Returns format for download
@@ -37,7 +38,13 @@ def get_format(format: str, quality: str) -> str:
         vres = f"[height<={quality}]" if quality != "best" else ""
         vcombo = vres + vfmt
 
-        return f"bestvideo{vcombo}+bestaudio{afmt}/best{vcombo}"
+        # iOS has strict requirements for video files, requiring h264 or h265
+        # video codec and aac audio codec in MP4 container. This format string
+        # attempts to get the fully compatible formats first, then the h264/h265
+        # video codec with any M4A audio codec (because audio is faster to
+        # convert if needed), and falls back to getting the best available MP4
+        # file.
+        return f"bestvideo[vcodec~='^((he|a)vc|h26[45])']{vres}+bestaudio[acodec=aac]/bestvideo[vcodec~='^((he|a)vc|h26[45])']{vres}+bestaudio{afmt}/bestvideo{vcombo}+bestaudio{afmt}/best{vcombo}"
 
     raise Exception(f"Unkown format {format}")
 
@@ -55,29 +62,41 @@ def get_opts(format: str, quality: str, ytdl_opts: dict) -> dict:
     Returns:
       ytdl_opts: Extra options
     """
-    
+
     opts = copy.deepcopy(ytdl_opts)
 
     postprocessors = []
 
     if format in AUDIO_FORMATS:
-        postprocessors.append({
-            "key": "FFmpegExtractAudio",
-            "preferredcodec": format,
-            "preferredquality": 0 if quality == "best" else quality,
-        })
+        postprocessors.append(
+            {
+                "key": "FFmpegExtractAudio",
+                "preferredcodec": format,
+                "preferredquality": 0 if quality == "best" else quality,
+            }
+        )
 
-        #Audio formats without thumbnail
+        # Audio formats without thumbnail
         if format not in ("wav") and "writethumbnail" not in opts:
             opts["writethumbnail"] = True
-            postprocessors.append({"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"})
+            postprocessors.append(
+                {
+                    "key": "FFmpegThumbnailsConvertor",
+                    "format": "jpg",
+                    "when": "before_dl",
+                }
+            )
             postprocessors.append({"key": "FFmpegMetadata"})
             postprocessors.append({"key": "EmbedThumbnail"})
-    
+
     if format == "thumbnail":
         opts["skip_download"] = True
         opts["writethumbnail"] = True
-        postprocessors.append({"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"})
-    
-    opts["postprocessors"] = postprocessors + (opts["postprocessors"] if "postprocessors" in opts else [])
+        postprocessors.append(
+            {"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"}
+        )
+
+    opts["postprocessors"] = postprocessors + (
+        opts["postprocessors"] if "postprocessors" in opts else []
+    )
     return opts