kalibrate-rtl | fork of http : //thre.at/kalibrate/ for use with rtl-sdr | Video Utils library
kandi X-RAY | kalibrate-rtl Summary
kandi X-RAY | kalibrate-rtl Summary
A base station transmits a frequency correction burst on the Frequency Correction CHannel (FCCH) in regular positions. The FCCH repeats every 51 TDMA frames and the frequency correction burst is located in timeslot 0 of frames 0, 10, 20, 30, and 40. A frequency correction burst consists of a certain bit pattern which, after modulation, is a sine wave with frequency one quarter that of the GSM bit rate. I.e., (1625000 / 6) / 4 = 67708.3 Hz. By searching a channel for this pure tone, a mobile station can determine its clock offset by determining how far away from 67708.3Hz the received frequency is. There are many ways which a pure tone can be identified. For example, one can capture a burst of data and then examine it with a Fourier transformation to determine if most of the power in the signal is at a certain frequency. Alternatively, one can define a band-pass filter at 67708.3 Hz and then compare the power of the signal before and after it passes through the filter. However, both of these methods have drawbacks. The FFT method requires significant resources and cannot easily detect the frequency correction burst edge. The filter method either isn’t accurate or cannot detect larger offsets. Multiple filters can be used, but that requires significant resources.
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Community Discussions
Trending Discussions on Video
QUESTION
This code is working for downloading all photos and videos
...ANSWER
Answered 2022-Feb-19 at 06:17Post has an is_video property
QUESTION
I don't want to show playback speed in my video, is there any controls or controlList properties to disable that option like controls disablepictureinpicture controlslist="nodownload"
ANSWER
Answered 2021-Sep-08 at 10:36According to the docs only three options are available (nodownload, nofullscreen, and noremoteplayback) and none seems to do what you want.
And you can't style the browser's default control set, but you can use the (JavaScript) Media API to build your own control set which of course you can style in any way that you like.
See this CodePen.
QUESTION
I imported a tif movie into python which has the dimensions (150,512,512). I would like to calculate the mean pixel intensity for each of the 150 frames and then plot it over time. I could figure out how to calculate the mean intensity over the whole stack (see below), but I am struggling to calculate it for each frame individually.
ANSWER
Answered 2022-Feb-18 at 23:25You could slice the matrix and obtain the mean for each frame like below
QUESTION
I'm trying to add rotation metadata to the video recorded from RTSP stream. All works fine until I try to run recording with segment format. My command looks like this:
...ANSWER
Answered 2022-Feb-11 at 10:03I found out it has been resolved in
and it works fine in ffmpeg 5.0. You can also apply this patch to 4.4.
QUESTION
I have several videos on my site that have the same class.
I want to play only one video when hovering over it. As soon as I removed the hover, the video was paused with a delay of 1 second.
I learned how to start a video and pause it. But as soon as I add setTimeout I get an error:
Uncaught TypeError: Cannot read properties of undefined (reading 'pause')
Below I am attaching the html code of my solution:
...ANSWER
Answered 2022-Feb-04 at 20:36The issue is because this in the setTimeout() function handler refers to that function, not to the element reference provided in the invocation of the outer hoverVideo() or hideVideo() functions.
To fix this issue create a variable in the outer scope to retain the reference to this which you use within the setTimeout():
QUESTION
I have an interlaced video stream and need apply a filter (any filter that takes two frames as input , for example tblend or lut2) on custom video frames and place output of them between mainframes like this :
...ANSWER
Answered 2022-Feb-04 at 10:13You may chain tblend, interleave and setpts filters, while the two inputs to interleave filter are the output of tblend and the original video:
Example (assuming input framerate is 25Hz):
QUESTION
I would like to be able to robustly stop a video when the video arrives on some specified frames in order to do oral presentations based on videos made with Blender, Manim...
I'm aware of this question, but the problem is that the video does not stops exactly at the good frame. Sometimes it continues forward for one frame and when I force it to come back to the initial frame we see the video going backward, which is weird. Even worse, if the next frame is completely different (different background...) this will be very visible.
To illustrate my issues, I created a demo project here (just click "next" and see that when the video stops, sometimes it goes backward). The full code is here.
The important part of the code I'm using is:
...ANSWER
Answered 2022-Jan-21 at 19:18The video has frame rate of 25fps, and not 24fps:
After putting the correct value it works ok: demo
The VideoFrame api heavily relies on FPS provided by you. You can find FPS of your videos offline and send as metadata along with stop frames from server.
The site videoplayer.handmadeproductions.de uses window.requestAnimationFrame() to get the callback.
There is a new better alternative to requestAnimationFrame. The requestVideoFrameCallback(), allows us to do per-video-frame operations on video.
The same functionality, you domed in OP, can be achieved like this:
QUESTION
In my Facebook Video Downloader android application i want to show video resolutions like SD, HD with size. Currently i am using InputStreamReader and Pattern.compile method to find SD and HD URL of video.
This method rarely gets me HD link of videos and provides only SD URL which can be downloaded.
Below is my code of link parsing
...ANSWER
Answered 2022-Jan-26 at 12:11Found a solution for this so posting as answer.
This can be done by extracting Page Source of a webpage and then parsing that XML and fetching list of BASE URLs.
Steps as follow:
1- Load that specific video URL in Webview and get Page Source inside onPageFinished
QUESTION
So I have a page with a grid layout, with a header and a footer and a black content container in the middle.
...ANSWER
Answered 2022-Jan-21 at 00:571fr
The first thing you need to know is that 1fr is equivalent to minmax(auto, 1fr), meaning that the container won't be smaller than its content, by default.
So, start by replacing 1fr with minmax(0, 1fr). That will solve the overflow problem.
QUESTION
I'm having regularly issue with hvc1 videos getting an inconsistent number of frames between ffprobe info and FFmpeg info, and I would like to know what could be the reason for this issue and how if it's possible to solve it without re-encoding the video.
I wrote the following sample script with a test video I have
I split the video into 5-sec segments and I get ffprobe giving the expected video length but FFmpeg gave 3 frames less than expected on every segment but the first one.
The issue is exactly the same if I split by 10 seconds or any split, I always lose 3 frames.
I noted that the first segment is always 3 frames smaller (on ffprobe) than the other ones and it's the only consistent one.
Here is an example script I wrote to test this issue :
...ANSWER
Answered 2022-Jan-11 at 22:08The source of the differences is that FFprobe counts the discarded packets, and FFmpeg doesn't count the discarded packets as frames.
Your results are consistent with video stream that is created with 3 B-Frames (3 consecutive B-Frames for every P-Frame or I-Frame).
According to Wikipedia:
I‑frames are the least compressible but don't require other video frames to decode.
P‑frames can use data from previous frames to decompress and are more compressible than I‑frames.
B‑frames can use both previous and forward frames for data reference to get the highest amount of data compression.
When splitting a video with P-Frame and B-Frame into segments without re-encoding, the dependency chain breaks.
- There are (almost) always frames that depends upon frames from the previous segment or the next segment.
- The above frames are kept, but the matching packets are marked as "discarded" (marked with
AV_PKT_FLAG_DISCARDflag).
For the purpose of working on the same dataset, we my build synthetic video (to be used as input).
Building synthetic video with the following command:
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