ax-devil-rtsp

Install

pip install ax-devil-rtsp

That is all: decoding uses PyAV, whose wheels bundle FFmpeg for Linux, macOS and Windows. No system packages are needed. pip install 'ax-devil-rtsp[display]' adds OpenCV for the CLI's video window.

ax-devil-rtsp doctor shows the PyAV and FFmpeg versions, whether the H.264 and H.265 decoders are present, and which hardware backends are compiled into FFmpeg. It also tries initializing the default hardware device for each backend with both decoders, without contacting a camera:

• READY: the default device initialized for this decoder.
• UNAVAILABLE: initialization failed, with the driver or permission error shown.
• UNSUPPORTED: this decoder has no hardware configuration for that backend.

Hardware decoding is optional and may need system GPU drivers. READY does not guarantee support for a particular stream's profile, bit depth or resolution, and does not prove frames were hardware-decoded. Hardware probe failures do not make doctor fail; missing H.264 or H.265 decoders do.

Python API

import time

from ax_devil_rtsp import SceneMetadata, StreamConfig, StreamSession, VideoOutput, VideoSample, build_axis_rtsp_url

config = StreamConfig(video=VideoOutput.RGB24, metadata=True)
url = build_axis_rtsp_url("192.168.1.90", config, username="root", password="secret", resolution="1280x720")


def on_video(sample: VideoSample) -> None:
    print("frame", sample.data.shape, "captured at", sample.capture_time_ns)


def on_metadata(document: SceneMetadata) -> None:
    print("metadata", len(document.xml), "characters, UtcTime", document.utc_time_ns)


with StreamSession(url, config, on_video=on_video, on_metadata=on_metadata) as session:
    time.sleep(10)
if session.failure:
    print("stream failed:", session.failure)

Sessions

• A StreamSession is one RTSP connection with a fixed StreamConfig. It receives at most one video and one scene metadata stream. It is one-shot: create a new session to reconnect.
• start() returns once the camera accepted PLAY. It raises StreamError when the connection, authentication or stream setup fails, or StartCancelledError if stop() was called first. with session: starts, then stops and waits on exit.
• stop() never blocks and may be called from callbacks. join() waits for the session to end.
• Sessions are independent; run as many as you need.

Callbacks and threads

Each session runs one receive thread. It reads the socket, reassembles RTP, decodes, converts and calls your callbacks one at a time, in stream order. There are no hidden queues: a slow callback slows only its own session, and the camera's TCP stream backs up instead of memory growing. Hand data to other threads yourself, and drop frames there if your consumer is slower than the camera.

A separate sender keeps RTSP alive even while media is idle or a callback is blocked. It never invokes callbacks and ends with the session. Stopping shuts down the TCP connection immediately rather than waiting to send TEARDOWN.

Every delivered value is owned by the receiver; keep it as long as you like.

If a callback raises, the session stops and that exception becomes session.failure. If the connection, the camera or decoding fails, failure is a StreamError whose message never contains credentials. Either is also passed to on_failure, once, if the session was already running.

What you receive

StreamConfig.video chooses what VideoSample.data is for the whole session:

VideoSample is generic, so typed callbacks can declare what they get, for example VideoSample[NDArray[np.uint8]]. Each sample also has the frame's rtp_timestamp, keyframe flag and capture_time_ns.

SceneMetadata holds one complete scene metadata XML document as xml, plus its rtp_timestamp and capture_time_ns. Parsing the XML is up to you.

StreamConfig.hwaccel names an FFmpeg hardware device type such as "vaapi" or "cuda" for decoding.

Matching video and metadata

With onvifreplayext=1 in the URL (on by default in build_axis_rtsp_url), the camera sends the capture time of every video frame. sample.capture_time_ns holds it in Unix nanoseconds. A scene metadata document names the frame it describes in its UtcTime attribute; document.utc_time_ns returns it. On Axis cameras the two agree within about a millisecond, the precision of UtcTime. ax-devil-rtsp stream prints this distance every second.

URLs

build_axis_rtsp_url(host, config, ...) builds an Axis axis-media/media.amp URL that asks for exactly the streams in config: analytics=polygon when metadata is requested, video=0 when video is not. Options: username, password, port, camera (video source), resolution and capture_time.

Any other RTSP URL is used as given, including its credentials. Only rtsp:// over TCP is supported.

If a metadata stream gives 400 Bad Request, the camera's scene metadata producer is probably disabled; enable AnalyticsSceneDescription for that channel, for example with ax-devil-device-api analytics-metadata enable AnalyticsSceneDescription -c 1.

Logging

The package logs through the standard logging module under the ax_devil_rtsp logger and configures no handlers.

CLI

Set AX_DEVIL_TARGET_ADDR, AX_DEVIL_TARGET_USER and AX_DEVIL_TARGET_PASS to skip the device options.

# Video and metadata; prints frame rate, capture-time coverage, metadata rate and sync once per second
ax-devil-rtsp stream --device-ip 192.168.1.90 --device-username root --device-password secret

# Show the video in a window (needs ax-devil-rtsp[display])
ax-devil-rtsp stream --display

# Metadata only, printing each document
ax-devil-rtsp stream --video none --print-xml

# Any RTSP URL, encoded video only
ax-devil-rtsp stream --url "rtsp://root:secret@192.168.1.90/axis-media/media.amp" --video encoded --no-metadata

ax-devil-rtsp doctor

Run ax-devil-rtsp stream --help for every option.

Development

python3 -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

pytest           # offline: a local fake camera serves real H.264/H.265 and metadata over RTSP
ruff check . && ruff format --check .
mypy

tools/bench.py measures CPU, memory, frame rate, latency and sync for one or more sessions against a real camera.

Disclaimer

This project is an independent, community-driven implementation and is not affiliated with or endorsed by Axis Communications AB. For official APIs and development resources, see the Axis Developer Community.

License

MIT License - see LICENSE for details.