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Médias (1)
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Rennes Emotion Map 2010-11
19 octobre 2011, par
Mis à jour : Juillet 2013
Langue : français
Type : Texte
Autres articles (59)
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Personnaliser en ajoutant son logo, sa bannière ou son image de fond
5 septembre 2013, parCertains thèmes prennent en compte trois éléments de personnalisation : l’ajout d’un logo ; l’ajout d’une bannière l’ajout d’une image de fond ;
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Publier sur MédiaSpip
13 juin 2013Puis-je poster des contenus à partir d’une tablette Ipad ?
Oui, si votre Médiaspip installé est à la version 0.2 ou supérieure. Contacter au besoin l’administrateur de votre MédiaSpip pour le savoir -
List of compatible distributions
26 avril 2011, parThe table below is the list of Linux distributions compatible with the automated installation script of MediaSPIP. Distribution nameVersion nameVersion number Debian Squeeze 6.x.x Debian Weezy 7.x.x Debian Jessie 8.x.x Ubuntu The Precise Pangolin 12.04 LTS Ubuntu The Trusty Tahr 14.04
If you want to help us improve this list, you can provide us access to a machine whose distribution is not mentioned above or send the necessary fixes to add (...)
Sur d’autres sites (6642)
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Extracting frames from a video does not work correctly [closed]
13 avril 2024, par Al TilmidhUsing the libraries (libav) and (ffmpeg), I try to extract frames as
.jpgfiles from avideo.mp4, the problem is that my program crashes when I use theCV_8UC3parameter, but by changing this parameter toCV_8UC1, the extracted images end up without color (grayscale), I don't really know what I missed, here is a minimal code to reproduce the two situations :

#include <opencv2></opencv2>opencv.hpp>

extern "C"
{
#include <libavformat></libavformat>avformat.h>
#include <libavcodec></libavcodec>avcodec.h>
}

int main()
{
 AVFormatContext *formatContext = nullptr;

 if (avformat_open_input(&formatContext, "video.mp4", nullptr, nullptr) != 0)
 {
 return -1;
 }

 if (avformat_find_stream_info(formatContext, nullptr) < 0)
 {
 return -1;
 }

 AVPacket packet;
 const AVCodec *codec = nullptr;
 AVCodecContext *codecContext = nullptr;

 int videoStreamIndex = av_find_best_stream(formatContext, AVMEDIA_TYPE_VIDEO, -1, -1, &codec, 0);
 if (videoStreamIndex < 0)
 {
 return -1;
 }

 codecContext = avcodec_alloc_context3(codec);
 avcodec_parameters_to_context(codecContext, formatContext->streams[videoStreamIndex]->codecpar);

 if (avcodec_open2(codecContext, codec, nullptr) < 0)
 {
 return -1;
 }

 AVFrame *frame = av_frame_alloc();

 while (av_read_frame(formatContext, &packet) >= 0)
 {
 if (packet.stream_index == videoStreamIndex)
 {
 int response = avcodec_send_packet(codecContext, &packet);
 
 if (response < 0)
 {
 break;
 }

 while (response >= 0)
 {
 response = avcodec_receive_frame(codecContext, frame);
 if (response == AVERROR(EAGAIN))
 {
 // NO FRAMES
 break;
 }

 else if (response == AVERROR_EOF)
 {
 // END OF FILE
 break;
 }

 else if (response < 0)
 {
 break;
 }

 //cv::Mat frameMat(frame->height, frame->width, CV_8UC3, frame->data[0]); // CV_8UC3 → THE PROGRAM CRASHES
 cv::Mat frameMat(frame->height, frame->width, CV_8UC1, frame->data[0]); // CV_8UC1 → WORK BUT IMAGES ARE IN GRAYSCALE
 cv::imwrite("frame_" + std::to_string(frame->pts) + ".jpg", frameMat);
 }
 }

 av_packet_unref(&packet);
 }

 av_frame_free(&frame);
 avcodec_free_context(&codecContext);
 avformat_close_input(&formatContext);

 return 0;
}


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Fast movie creation using MATLAB and ffmpeg
24 février 2018, par hyiltizI have some time series data that I would like to create into movies. The data could be 2D (about 500x10000) or 3D (500x500x10000). For 2D data, the movie frames are simply line plot using
plot, and for 3D data, we can usesurf,imagesc,contouretc. Then we create a video file using these frames in MATLAB, then compress the video file usingffmpeg.To do it fast, one would try not to render all the images to display, nor save the data to disk then read it back again during the process. Usually, one would use
getframeorVideoWriterto create movie in MATLAB, but they seem to easily get tricky if one tries not to display the figures to screen. Some even suggest plotting in hidden figures, then saving them as images to disk as.pngfiles, then compress them usingffmpeg(e.g. withx265encoder into.mp4). However, saving the output ofimagescin my iMac took 3.5s the first time, then 0.5s after. I also find it not fast enough to save so many files to disk only to askffmpegto read them again. One couldhardcopythe data as this suggests, but I am not sure whether it works regardless of the plotting method (e.g.plot,surfetc.), and how one would transfer data over toffmpegwith minimal disk access.This is similiar to this, but
immovieis too slow. This post 3 is similar, but advocates writing images to disk then reading them (slow IO). -
Rails ActionController::Live - Sends everything at once instead of async
28 janvier 2016, par Michael BI have an issue with rails
ActionController::LiveIn the end I want to show the progress of FFMPEG to the user, but for now I want to get this minimal example running :
Rails media_controller.rb :
class MediaController < ApplicationController
include ActionController::Live
def stream
puts "stream function loaded"
response.headers['Content-Type'] = 'text/event-stream'
i = 0
begin
response.stream.write "data: 1\n\n"
sleep 0.5
i += 1
puts "response... data: " + i.to_s
end while i < 10
response.stream.close
end
endJavascript :
source = new EventSource("/test/0");
source.addEventListener("message", function(response) {
// Do something with response.data
console.log('I have received a response from the server: ' + response);
}, false);When I navigate to the site, there are no JavaScript Errors showing. As soon as I navigate to the site, the "stream"-Action of the MediaController gets successfully called. I can verify this, by looking at the Server-Console. It gives me the following output. After every response line, there is a 500ms delay, like expected :
stream function loaded
response... data: 1
response... data: 2
response... data: 3
response... data: 4
response... data: 5
response... data: 6
response... data: 7
response... data: 8
response... data: 9
response... data: 10
Completed 200 OK in 5005ms (ActiveRecord: 0.8ms)On the JavaScript Side, it gives me the following Output :
(10x) I have received a response from the server: [object MessageEvent]But the problem is here, that it sends all these 10 Messages from the server after 5 seconds at the same time ! The expected behavior however is, that it should send me 1 message every 0.5 seconds !
So what am I doing wrong here ? Where is the error ?
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