Audio/Video

How to fix dji_irp: error while loading shared libraries: libdirp.so: cannot open shared object file: No such file or directory

Problem:

When you try to run dji_irp from the DJI thermal SDK on Linux, you see the following error message:

./utility/bin/linux/release_x64/dji_irp: error while loading shared libraries: libdirp.so: cannot open shared object file: No such file or directory

Solution:

The libdirp.so library is included with the SDK but it is in a subfolder (the same subfolder where dji_irp is located) where the shell can’t find it.

In order to fix the issue, prefix the command you’re using with

LD_LIBRARY_PATH=./utility/bin/linux/release_x64/

For example:

LD_LIBRARY_PATH=./utility/bin/linux/release_x64/ ./utility/bin/linux/release_x64/dji_irp

 

 

Posted by Uli Köhler in Audio/Video, Linux

Raspberry Pi libcamera VLC recording to H.264 (1920×1080)

On the Pi, run

libcamera-vid -t 0 --width 1920 --height 1080 --codec h264 -o out.h264

This will record Full-HD video (1920×1080) to out.h264

Posted by Uli Köhler in Audio/Video, Raspberry Pi

How to list available cameras on Raspberry Pi (libcamera)

Use this command to list all available cameras:

libcamera-still --list-cameras

Example output:

$ libcamera-still --list-cameras
Available cameras
-----------------
0 : imx477 [4056x3040] (/base/soc/i2c0mux/[email protected]/[email protected])
    Modes: 'SRGGB10_CSI2P' : 1332x990 [120.05 fps - (696, 528)/2664x1980 crop]
           'SRGGB12_CSI2P' : 2028x1080 [50.03 fps - (0, 440)/4056x2160 crop]
                             2028x1520 [40.01 fps - (0, 0)/4056x3040 crop]
                             4056x3040 [10.00 fps - (0, 0)/4056x3040 crop]

 

Posted by Uli Köhler in Audio/Video, Raspberry Pi

How to fix Raspberry Pi OS raspivid: command not found

Problem:

When trying to run raspivid on Raspberry Pi OS Lite, you will see the following error message:

bash: raspivid: command not found

Solution:

In recent versions of Raspberry Pi OS, raspivid has been replaced by libcamera-vid. Therefore, use libcamera-vid instead of raspivid.

Posted by Uli Köhler in Audio/Video, Raspberry Pi

How to set and verify v4l2-ctl parameters in Python using subprocess

The following code uses the v4l2-ctl executable to get and set v4l2 parameters such as exposure_absolute. It also provides means of writing a parameter and verifying if it has been set correctly.

def v4l2_set_parameters_once(params, device="/dev/video0"):
    """
    Given a dict of parameters:
    {
        "exposure_auto": 1,
        "exposure_absolute": 10,
    }
    this function sets those parameters using the v4l2-ctl command line executable
    """
    set_ctrl_str = ",".join([f"{k}={v}" for k,v in params.items()]) # expsosure_absolute=400,exposure_auto=1
    subprocess.check_output(["v4l2-ctl", "-d", device, f"--set-ctrl={set_ctrl_str}"])

def v4l2_get_parameters(params, device="/dev/video0"):
    """
    Query a bunch of v4l2 parameters.
    params is a list like
    [
        "exposure_auto",
        "exposure_absolute"
    ]
    
    Returns a dict of values:
    {
        "exposure_auto": 1,
        "exposure_absolute": 10,
    }
    """
    get_ctrl_str = ",".join([f"{k}" for k in params])
    out = subprocess.check_output(["v4l2-ctl", "-d", device, f"--get-ctrl={get_ctrl_str}"])
    out = out.decode("utf-8")
    result = {}
    for line in out.split("\n"):
        # line should be like "exposure_auto: 1"
        if ":" not in line:
            continue
        k, _, v = line.partition(":")
        result[k.strip()] = v.strip()
    return result

def v4l2_set_params_until_effective(params, device="/dev/video0"):
    """
    Set V4L2 params and check if they have been set correctly.
    If V4L2 does not confirm the parameters correctly, they will be set again until they have an effect
    
    params is a dict like {
        "exposure_auto": 1,
        "exposure_absolute": 10,
    }
    """
    while True:
        v4l2_set_parameters_once(params, device=device)
        result = v4l2_get_parameters(params.keys(), device=device)
        # Check if queried parameters match set parameters
        had_any_mismatch = False
        for k, v in params.items():
            if k not in result:
                raise ValueError(f"Could not query {k}")
            # Note: Values from v4l2 are always strings. So we need to compare as strings
            if str(result.get(k)) != str(v):
                print(f"Mismatch in {k} = {result.get(k)} but should be {v}")
                had_any_mismatch = True
        # Check if there has been any mismatch
        if not had_any_mismatch:
            return

Usage example:

v4l2_set_params_until_effective({
    "exposure_auto": 1,
    "exposure_absolute": 1000,
})

 

Posted by Uli Köhler in Audio/Video, Linux, OpenCV, Python

How are OpenCV CAP_PROP_… mapped to V4L2 ctrls / parameters?

From both the OpenCV documentation and the V4L2 documentation, it is unclear how all the CAP_PROP_... parameters are mapped to v4l2 controls such as exposure_absolute.

However, you can easily look in the source code (int capPropertyToV4L2(int prop) in cap_v4l.cpp) in order to see how the parameters are mapped internally. Github link to the source code

Continue reading →

Posted by Uli Köhler in Audio/Video, Linux, OpenCV

How to get length/duration of video file in Python using ffprobe

In our previous post How to get video metadata as JSON using ffmpeg/ffprobe we showed how to generate json-formatted output using ffprobe which comes bundled with ffmpeg.

Assuming ffprobe is installed, you can easily use this to obtain the duration of a video clip (say, in  input.mp4) using Python:

import subprocess
import json

input_filename = "input.mp4"

out = subprocess.check_output(["ffprobe", "-v", "quiet", "-show_format", "-print_format", "json", input_filename])

ffprobe_data = json.loads(out)
duration_seconds = float(ffprobe_data["format"]["duration"])
# Example: duration_seconds = 11.6685

When writing such code, be aware of the risk of shell code injection if you don’t using subprocess correctly!

Posted by Uli Köhler in Audio/Video, Python

How to get video metadata as JSON using ffmpeg/ffprobe

You can easily use ffprobe to extract metadata from a given video file (input.mp4 in this example):

ffprobe -v quiet -show_format -show_streams -print_format json input.mp4

Depending on what info you need, you can also omit -show_streams which doesn’t print detailed codec info for the Audio/Video streams but just general data about the file:

ffprobe -v quiet -show_format -print_format json input.mp4

Example output (without -show-streams):

{
    "format": {
        "filename": "input.mp4",
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
        "format_long_name": "QuickTime / MOV",
        "start_time": "0.000000",
        "duration": "11.668500",
        "size": "25045529",
        "bit_rate": "17171378",
        "probe_score": 100,
        "tags": {
            "major_brand": "mp42",
            "minor_version": "0",
            "compatible_brands": "isommp42",
            "creation_time": "2022-10-20T19:00:13.000000Z",
            "location": "+48.1072+011.7441/",
            "location-eng": "+48.1072+011.7441/",
            "com.android.version": "12",
            "com.android.capture.fps": "30.000000"
        }
    }
}

 

Example output (with -show_streams):

{
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "High",
            "codec_type": "video",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 1920,
            "height": 1080,
            "coded_width": 1920,
            "coded_height": 1080,
            "closed_captions": 0,
            "has_b_frames": 0,
            "pix_fmt": "yuv420p",
            "level": 40,
            "color_range": "tv",
            "color_space": "bt709",
            "color_transfer": "bt709",
            "color_primaries": "bt709",
            "chroma_location": "left",
            "refs": 1,
            "is_avc": "true",
            "nal_length_size": "4",
            "r_frame_rate": "30/1",
            "avg_frame_rate": "10170000/349991",
            "time_base": "1/90000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 1049973,
            "duration": "11.666367",
            "bit_rate": "16914341",
            "bits_per_raw_sample": "8",
            "nb_frames": "339",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "rotate": "90",
                "creation_time": "2022-10-20T19:00:13.000000Z",
                "language": "eng",
                "handler_name": "VideoHandle",
                "vendor_id": "[0][0][0][0]"
            },
            "side_data_list": [
                {
                    "side_data_type": "Display Matrix",
                    "displaymatrix": "\n00000000:            0       65536           0\n00000001:       -65536           0           0\n00000002:            0           0  1073741824\n",
                    "rotation": -90
                }
            ]
        },
        {
            "index": 1,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "LC",
            "codec_type": "audio",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "48000",
            "channels": 2,
            "channel_layout": "stereo",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/48000",
            "start_pts": 2016,
            "start_time": "0.042000",
            "duration_ts": 558071,
            "duration": "11.626479",
            "bit_rate": "256234",
            "nb_frames": "545",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            },
            "tags": {
                "creation_time": "2022-10-20T19:00:13.000000Z",
                "language": "eng",
                "handler_name": "SoundHandle",
                "vendor_id": "[0][0][0][0]"
            }
        }
    ],
    "format": {
        "filename": "input.mp4",
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
        "format_long_name": "QuickTime / MOV",
        "start_time": "0.000000",
        "duration": "11.668500",
        "size": "25045529",
        "bit_rate": "17171378",
        "probe_score": 100,
        "tags": {
            "major_brand": "mp42",
            "minor_version": "0",
            "compatible_brands": "isommp42",
            "creation_time": "2022-10-20T19:00:13.000000Z",
            "location": "+48.1072+011.7441/",
            "location-eng": "+48.1072+011.7441/",
            "com.android.version": "12",
            "com.android.capture.fps": "30.000000"
        }
    }
}
u

 

Posted by Uli Köhler in Audio/Video

How to rotate video by 90°/180°/270° using ffmpeg

In order to rotate a video named input.mp4 using ffmpeg, use the following commands:

Rotate by 90° (clockwise)

ffmpeg -i input.mp4 -vf "transpose=1" rotated.mp4

Rotate by 180°

ffmpeg -i input.mp4 -vf "transpose=2" rotated.mp4

Rotate by 270° (clockwise)

This is equivalent to rotating 90° counter-clockwise.

ffmpeg -i input.mp4 -vf "transpose=3" rotated.mp4

 

Posted by Uli Köhler in Audio/Video

How to install avidemux3 on Ubuntu 22.04

You can install Avidemux 3 (QT) from the xtradebs PPA:

sudo apt -y install software-properties-common apt-transport-https -y
sudo add-apt-repository -y ppa:xtradeb/apps
sudo apt -y install avidemux-qt

After that, run

avidemux3_qt5

to run Avidemux 3.

Posted by Uli Köhler in Audio/Video, Linux

How to re-encode all videos in a directory as H.265 & opus using ffmpeg

In our previous post How to re-encode videos as H.265 & opus using ffmpeg for archival we listed ffmpeg commands to re-encode video files to H.265 for archival purposes.

In many cases, you want to re-encode all files in a directory. The following example command (for Linux shell such as bash) re-encodes every .avi file in the current directory, assuming that all files are non-interlaced (this affects the ffmpeg flags – see our previous post for more details).

for i in *.avi ; do ffmpeg -i "$i" -c:v libx265 -crf 26 -c:a libopus -b:a 56k -frame_duration 60 "${i}.mkv" ; done

From mymovie.avi, this script will produce mymovie.avi.mkv, saving approximately 70% of the filesize (that, of course, depends heavily on the video itself).

You can easily adapt this command to your liking – for example, by encoding .mp4 files instead of .avi or usign a different CRF or audio bitrate. However, in my opinion, these are sane defaults for most video where the focus is to find a compromise between good video quality and file sie.

Posted by Uli Köhler in Audio/Video

How to query all camera parameters using v4l2-ctl

You can query all parameters using v4l2-ctl‘s --all parameter, for example:

v4l2-ctl --device /dev/video0 --all

 

Posted by Uli Köhler in Audio/Video

How to always get latest frame from OpenCV VideoCapture in Python

When working with OpenCV video capture, but when you only occasionally use images, you will get older images from the capture buffer.

This code example solves this issue by running a separate capture thread that continually saves images to a temporary buffer.

Therefore, you can always get the latest image from the buffer. The code is based on our basic example How to take a webcam picture using OpenCV in Python

video_capture = cv2.VideoCapture(0)

video_capture.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)
video_capture.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)

if not video_capture.isOpened():
    raise Exception("Could not open video device")

class TakeCameraLatestPictureThread(threading.Thread):
    def __init__(self, camera):
        self.camera = camera
        self.frame = None
        super().__init__()
        # Start thread
        self.start()

    def run(self):
        while True:
            ret, self.frame = self.camera.read()

latest_picture = TakeCameraLatestPictureThread(video_capture)

Usage example:

# Convert latest image to the correct colorspace
rgb_img = cv2.cvtColor(latest_picture.frame, cv2.COLOR_BGR2RGB)
# Show
plt.imshow(rgb_img)

 

 

Posted by Uli Köhler in Audio/Video, OpenCV, Python

How to capture single PNG image using fswebcam

fswebcam -r 1920x1080 --png 9 -d /dev/video0 -D 0 test.png

where:

  • -r 1920x1080 is the resolution of the image. The camera must support this. In order to see supported resolutions, see How to list USB camera video formats using v4l2-ctl
  • --png 9 means output PNG with quality 9PNG is lossless, so the quality is just the compression factor. 9 means accept higher CPU consumption for slightly smaller filesize.
  • -d /dev/video0 means to use the camera in /dev/video0
  • -D 0 means no delay before capturing the image
  • test.png means: Write the image to test.png.
Posted by Uli Köhler in Audio/Video

How to list USB camera video formats using v4l2-ctl

v4l2-ctl --device /dev/video0 --list-formats-ext

 

Posted by Uli Köhler in Audio/Video

How to get Jitsi meet list of participants using Tapermonkey script

Use this code in Javascript:

APP.conference.listMembers()

If no members are present, this will simply be an empty list:

> APP.conference.listMembers()
[]

But if there is another participant, it will show some info:

> APP.conference.listMembers()
[ci]
0: ci {_jid: '[email protected]/b009ae10', _id: 'b009ae10', _conference: nd, _displayName: 'Foo', _supportsDTMF: false, …}
length: 1

 

Posted by Uli Köhler in Audio/Video, Javascript

How to autojoin Jitsi Meet meeting using Tapermonkey script

This code clicks the join button:

document.querySelector(".prejoin-preview-dropdown-container div[role='button']").click()

By using the correct @match, you can activate this only for a specific conference:

Complete script:

// ==UserScript==
// @name         AutojoinJitsiMeet
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  ?
// @author       You
// @match        https://meet.jit.si/TestAutoJoin
// @icon         https://www.google.com/s2/favicons?sz=64&domain=tampermonkey.net
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    document.querySelector(".prejoin-preview-dropdown-container div[role='button']").click()
})();

 

Posted by Uli Köhler in Audio/Video, Javascript

Fullscreen camera view using libcamera-vid

libcamera-vid --width 1920 --height 1080 -f -t 10000000000

-t 10000000000 means to run for 10000000000 milliseconds (almost 4 months)

Posted by Uli Köhler in Audio/Video, Electronics, Raspberry Pi

How to fix raspistill ERROR: the system should be configured for the legacy camera stack

Problem:

While trying to capture an image using raspistill, you see the following error message

ERROR: the system should be configured for the legacy camera stack

and no image is being produced

Solution 1 (recommended): Use libcamera

Recent versions of Raspbian use libcamera instead of the broadcom legacy camera API. You can capture an image using libcamera-still similarly to raspistill:

libcamera-still -o test.jpg

Solution 2: Enable legacy camera API

If you absolutely need raspistill specifically to work, you can still enable the legacy camera API using rpi-config:

sudo raspi-config

Go to:

  • 3 Interface Config
  • I1 Legacy Camera

and choose Yes to enable the legacy camera API.

Posted by Uli Köhler in Audio/Video, Raspberry Pi

Raspberry Pi libcamera VLC livestreaming (1920×1080)

On the Pi, run

libcamera-vid -t 0 --width 1920 --height 1080 --codec h264 --inline --listen -o tcp://0.0.0.0:8888

On the client, run

vlc tcp/h264://192.168.1.185:8888/

where 192.168.1.185 is the IP address of the Raspberry Pi.

Posted by Uli Köhler in Audio/Video, Raspberry Pi