So I know that one can adjust the rate of download with youtube-dl using the -r or --limit-rate flags; however, as part of a simulation testing, I am trying to simulate a user watching a video , and so I want to download a video at a rate such that the download would take as long as the video's duration is if one were to watch the video, so that a 2min long video would take 2min to download, and so on and so forth.
I have meticulously reviewed the available options on their github page, but it seems like there are no options natively to do that. But then the next best thing I can think of is to get the video duration in seconds (lets call it t) and the video size in bytes (lets call it s) and then use s/t as a value for the --limit-rate flag.
However now the problem is that there doesn't seem to be any options/flags to get the video file-size in bytes!
Is there anyway I can accomplish what my goal is here? I am open to using other tools/programs if this is outside the capabilities of youtube-dl.
To be more specific, I am working in linux server environment (no video-card and needs to be able headlessly), and the videos I'm dealing with are MPEG Dash videos from an MPD file, so whatever tool I use needs to be able to parse and work with MPD files.
Thank you for your help,
Related
I'm working on a c++ project that generates frames to be converted to a video later.
The project currently dumps all frames as jpg or png files in a folder and then I run ffmpeg manually to generate a mp4 video file.
This project runs on a web server and an ios/android app (under development) will call this web server to have the video generated and downloaded.
The web service is pretty much done and working fine.
I don't like this approach for obvious reasons like a server dependency, cost etc...
I successfully created a POC that exposes the frame generator lib to android and I got it to save the frames in a folder, my next step now is to convert it to video. I considered using any ffmpeg for android/ios lib and just call it when the frames are done.
Although it seems like I fixed half of the problem, I found a new one which is... each frame depending on the configuration could end up having 200kb+ in size, so depending on the amount of frames, it will take a lot of space from the user's device.
I'm sure this will become a huge problem very easily.
So I believe that the ideal solution would be to generate the mp4 file on demand as each frame is created, so in the end there would be no storage space being taken as I woudn't need to save a file for the frame.
The problem is that I don't know how to do that, I don't know much about ffmpeg, I know it's open source but I have no idea how to include a reference to it from the frames generator and generate the video "on demand".
I heard about libav as well but again, same problem...
I would really appreciate any sugestion on how to do it. What I need is basically a way to generate a mp4 video file given a list of frames.
thanks for any help!
I'm trying to develop a little application in which you can load a mp3 file and play it in variable speeds! (I know it already exists :-) )
I'm using Qt and C++. I already have the basic player but I'm stuck with the rate thing, because I want to change the rate smoothly (like in Mixxx) without stopping the playback! The QMediaPlayer always stops if I change the value and creates a gap in the sound. Also I don't want the pitch to change!
I already found something called "SoundTouch" but now I'm completely clueless what to do with it, how to process my mp3 data and how to get it to the player! The "SoundTouch" Library is capable of doing what I want, i got that from the samples on the homepage.
How do I have to import the mp3 file, so I can process it with the SoundTouch functions
How can I play the output from the SoundTouch function? (Perhaps QMediaPlayer can do the job?)
How is that stuff done live? I have to do some kind of stream I guess? So I can change the speed during play and keep on playing without gaps. Graphicaly in my head it has to be something that sits between the data and the player, where all data has to go through live, with a small buffer (20-50 ms or so) behind to avoid gaps during processing future data.
Any help appreciated! I'm also open to any another solution then "SoundTouch" as long as I can stay with Qt/C++!
(Second thing: I want to view a waveform overview aswell as moving part of it (around actual position of the song), so I could also use hints on how to get the waveform data)
Thanks in advance!
As of now (Qt 5.5) this is impossible to do with QMediaPlayer only. You need to do the following:
Decode the audio using GStreamer, FFMpeg or (new) QAudioDecoder: http://doc.qt.io/qt-5/qaudiodecoder.html - this will give you raw PCM stream;
Apply SoundTouch or some other library to this raw data to change the pitch. If GPL is ok, take a look at http://nsound.sourceforge.net/examples/index.html, if you develop proprietary stuff, STK might be a better choice: https://ccrma.stanford.edu/software/stk/
Output the modified data into audio device by using QAudioOutput.
This strategy uses Qt as much as possible, and brings you the best platform coverage (you still lose Android though as it does not support QAudioOutput)
In my fun project, I'm downloading video file from youtube, and writing to a file on local disk. Simultaneously I want to play it. The objective is to cache the file on local disk, so that when I want to see the video again, the app can play it locally, thereby saving bandwidth.
I'm using Python 3.3.1, PyQt4/Phonon and LibVLC. So far, I'm able to do the following things:
Given a youtube watch url, I can download the video file and then play it using both PyQt4/Phonon and LibVLC, independently. It is not streaming.
Since LibVLC supports streaming, I'm able to play the given url through streaming.
The second is very close to what I want to do, but since it doesn't save the file on disk, next time I cannot play the same video locally.
I'm looking for some guidelines as to how to proceed from here. In particular, how to play a video from an incomplete file which is still being written into.
I'm completely fine with any API (that does the job) as long as it is:
Python 3.3.1 (preferably)
C
C++.
And I'm looking for alternative approaches also, if my current approach is not correct or makes the problem more difficult than it actually is.
VLC supports playback of incomplete files, so if you're up for a bit of non-blocking I/O and/or parallel code, you should be able to start the download and after a sufficient amount has been written, use LibVLC to start playback. Depending on what compression algorithm is used, you may need to buffer enough so that there's always several seconds of data left in the buffer -- if I recall correctly, some of the more modern algorithms record deltas and index information going forward and backward.
You may get a few warnings / error messages / Exceptions, but I would not assume that they're fatal -- let the playback quality be your guide!
This is somewhat similar to some of the suggestions from the comments above, and is also related to a lot of what #abarnert said, to a lesser extent some of the exchange with #StackedCrooked.
We already have a functionality of Video uploading in our webapplication[built using python with Django framework]. Now we are in the process of building a livestream site where people are able to use their webcam to record the live event and it's live streamed to different participants at the sametime.
I am wondering if somebody has any idea of how to go about building a functionality like this or any pointers that would be really helpful.
I sort of looked into this same question a while ago. The dominant solution seems to be Adobes Flash Media Server. It is closed source of course and quite pricey. There are companies who run it as a service, lowering the cost of entry. And there are open source contenders, the main one being Red5, which of course also relies on flash being available on the client side.
In the future we'll probably see viable HTML5 alternatives but if you're doing something right now my feeling is that the flash route is the simplest solution and has the largest install base.
I did a video vlc record with python and it was quite simple. VLC have a stream recorder and as I know you could launch a vlc stream with a simple python code who manage the video ans the stream. I think all you need is to manage the sources and then, doing a small script who takes care about the vlc stream.
VLC stream will be launch on a different port, so I think you've to search a good server.
see vlc docs :
https://wiki.videolan.org/Documentation:Streaming_HowTo/Command_Line_Examples/
Enjoy :)
Check VLC or Flumotion...
Probably Photolab as well..
The latter one doesn't support audio...
Gee
I'm working on an audio creation framework. It'll be generating large audio files, say 3 minute long audio files that take about 1 minute to generate. So what I want is a system much like streaming audio from the internet, where I play the sound as I generate it.
Pygame's mixer allows me to edit the sound as it's playing. But I cannot figure out how to change the sample rate, sample size, or number of channels.
Snack allows me to edit sounds, as well as their sample rate, sample size, length, and number of channels. But I cannot figure out how to edit sounds as they are playing.
Could anybody point me to a library that allows me to edit a sound as it is playing, as well as configure the number of channels, sample rate, and length (all known ahead of time)? If not, perhaps somebody knows of a tutorial to do this in C++?
[EDIT] Pymedia.audio would work fine for me. However, I can't get it to work under Python 2.6. Any ideas?
pymedia.audio does work with Python 2.6. Take a look at this SO post: Pymedia installation on Windows with Python 2.6
You can append audio to Output objects, as they are playing. So as each sample is generated, it can also be appended to the stream. The example in their documentation shows just how to do this: http://pymedia.org/docs/pymedia.audio.sound.html