Remove pts adjustments in stream (#42399)

* Remove unnecessary pts adjustments

* Add comments

* Use -inf for initial last_dts to be more clear

* Use video first_pts as common adjuster in recorder

* Remove seek(0) before av.open

homeassistant/components/stream/recorder.py

@@ -25,12 +25,23 @@ def recorder_save_worker(file_out: str, segments: List[Segment], container_forma
     output_v = None
     output_a = None
 
-    for segment in segments:
-        # Seek to beginning and open segment
-        segment.segment.seek(0)
+    # Get first_pts values from first segment
+    if len(segments) > 0:
+        segment = segments[0]
         source = av.open(segment.segment, "r", format=container_format)
         source_v = source.streams.video[0]
+        first_pts["video"] = source_v.start_time
+        if len(source.streams.audio) > 0:
+            source_a = source.streams.audio[0]
+            first_pts["audio"] = int(
+                source_v.start_time * source_v.time_base / source_a.time_base
+            )
+        source.close()
 
+    for segment in segments:
+        # Open segment
+        source = av.open(segment.segment, "r", format=container_format)
+        source_v = source.streams.video[0]
         # Add output streams
         if not output_v:
             output_v = output.add_stream(template=source_v)
@@ -42,13 +53,12 @@ def recorder_save_worker(file_out: str, segments: List[Segment], container_forma
 
         # Remux video
         for packet in source.demux():
-            if packet is not None and packet.dts is not None:
-                if first_pts[packet.stream.type] is None:
-                    first_pts[packet.stream.type] = packet.pts
-                packet.pts -= first_pts[packet.stream.type]
-                packet.dts -= first_pts[packet.stream.type]
-                packet.stream = output_v if packet.stream.type == "video" else output_a
-                output.mux(packet)
+            if packet.dts is None:
+                continue
+            packet.pts -= first_pts[packet.stream.type]
+            packet.dts -= first_pts[packet.stream.type]
+            packet.stream = output_v if packet.stream.type == "video" else output_a
+            output.mux(packet)
 
         source.close()
 

homeassistant/components/stream/worker.py

@@ -102,11 +102,8 @@ def _stream_worker_internal(hass, stream, quit_event):
 
     # Iterator for demuxing
     container_packets = None
-    # The presentation timestamps of the first packet in each stream we receive
-    # Use to adjust before muxing or outputting, but we don't adjust internally
-    first_pts = {}
     # The decoder timestamps of the latest packet in each stream we processed
-    last_dts = None
+    last_dts = {video_stream: float("-inf"), audio_stream: float("-inf")}
     # Keep track of consecutive packets without a dts to detect end of stream.
     missing_dts = 0
     # Holds the buffers for each stream provider
@@ -123,21 +120,19 @@ def _stream_worker_internal(hass, stream, quit_event):
     # 2 - seeking can be problematic https://trac.ffmpeg.org/ticket/7815
 
     def peek_first_pts():
-        nonlocal first_pts, audio_stream, container_packets
-        missing_dts = 0
-
-        def empty_stream_dict():
-            return {
-                video_stream: None,
-                **({audio_stream: None} if audio_stream else {}),
-            }
+        """Initialize by peeking into the first few packets of the stream.
 
+        Deal with problem #1 above (bad first packet pts/dts) by recalculating using pts/dts from second packet.
+        Also load the first video keyframe pts into segment_start_pts and check if the audio stream really exists.
+        """
+        nonlocal segment_start_pts, audio_stream, container_packets
+        missing_dts = 0
+        found_audio = False
         try:
             container_packets = container.demux((video_stream, audio_stream))
-            first_packet = empty_stream_dict()
-            first_pts = empty_stream_dict()
+            first_packet = None
             # Get to first video keyframe
-            while first_packet[video_stream] is None:
+            while first_packet is None:
                 packet = next(container_packets)
                 if (
                     packet.dts is None
@@ -148,13 +143,17 @@ def empty_stream_dict():
                         )
                     missing_dts += 1
                     continue
-                if packet.stream == video_stream and packet.is_keyframe:
-                    first_packet[video_stream] = packet
+                if packet.stream == audio_stream:
+                    found_audio = True
+                elif packet.is_keyframe:  # video_keyframe
+                    first_packet = packet
                     initial_packets.append(packet)
             # Get first_pts from subsequent frame to first keyframe
-            while any(
-                [pts is None for pts in {**first_packet, **first_pts}.values()]
-            ) and (len(initial_packets) < PACKETS_TO_WAIT_FOR_AUDIO):
+            while segment_start_pts is None or (
+                audio_stream
+                and not found_audio
+                and len(initial_packets) < PACKETS_TO_WAIT_FOR_AUDIO
+            ):
                 packet = next(container_packets)
                 if (
                     packet.dts is None
@@ -165,24 +164,19 @@ def empty_stream_dict():
                         )
                     missing_dts += 1
                     continue
-                if (
-                    first_packet[packet.stream] is None
-                ):  # actually video already found above so only for audio
-                    if packet.is_keyframe:
-                        first_packet[packet.stream] = packet
-                    else:  # Discard leading non-keyframes
-                        continue
-                else:  # This is the second frame to calculate first_pts from
-                    if first_pts[packet.stream] is None:
-                        first_pts[packet.stream] = packet.dts - packet.duration
-                        first_packet[packet.stream].pts = first_pts[packet.stream]
-                        first_packet[packet.stream].dts = first_pts[packet.stream]
+                if packet.stream == audio_stream:
+                    found_audio = True
+                elif (
+                    segment_start_pts is None
+                ):  # This is the second video frame to calculate first_pts from
+                    segment_start_pts = packet.dts - packet.duration
+                    first_packet.pts = segment_start_pts
+                    first_packet.dts = segment_start_pts
                 initial_packets.append(packet)
-            if audio_stream and first_packet[audio_stream] is None:
+            if audio_stream and not found_audio:
                 _LOGGER.warning(
                     "Audio stream not found"
                 )  # Some streams declare an audio stream and never send any packets
-                del first_pts[audio_stream]
                 audio_stream = None
 
         except (av.AVError, StopIteration) as ex:
@@ -212,9 +206,6 @@ def initialize_segment(video_pts):
             )
 
     def mux_video_packet(packet):
-        # adjust pts and dts before muxing
-        packet.pts -= first_pts[video_stream]
-        packet.dts -= first_pts[video_stream]
         # mux packets to each buffer
         for buffer, output_streams in outputs.values():
             # Assign the packet to the new stream & mux
@@ -223,9 +214,6 @@ def mux_video_packet(packet):
 
     def mux_audio_packet(packet):
         # almost the same as muxing video but add extra check
-        # adjust pts and dts before muxing
-        packet.pts -= first_pts[audio_stream]
-        packet.dts -= first_pts[audio_stream]
         for buffer, output_streams in outputs.values():
             # Assign the packet to the new stream & mux
             if output_streams.get(audio_stream):
@@ -241,8 +229,8 @@ def finalize_stream():
     if not peek_first_pts():
         container.close()
         return
-    last_dts = {k: v - 1 for k, v in first_pts.items()}
-    initialize_segment(first_pts[video_stream])
+
+    initialize_segment(segment_start_pts)
 
     while not quit_event.is_set():
         try: