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The Slip - Artworks
26 septembre 2011, par
Mis à jour : Septembre 2011
Langue : English
Type : Texte
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Podcasting Legal guide
16 mai 2011, par
Mis à jour : Mai 2011
Langue : English
Type : Texte
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Creativecommons informational flyer
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Mis à jour : Juillet 2013
Langue : English
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Autres articles (96)
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MediaSPIP 0.1 Beta version
25 avril 2011, parMediaSPIP 0.1 beta is the first version of MediaSPIP proclaimed as "usable".
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To get a working installation, you must manually install all-software dependencies on the server.
If you want to use this archive for an installation in "farm mode", you will also need to proceed to other manual (...) -
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Problèmes fréquents
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Sur d’autres sites (5024)
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Can´t convert .mp4 file to .mjpeg file with ffmpeg
19 février 2018, par Herr HupfDohleI use ffmpeg to convert a .mp4 file to a .mjpeg file and I fail doing so.
What i tried so far :
Converting directly from .mp4 to .mjpeg with one of these :"ffmpeg -i input.mp4 output.mjpeg"
"ffmpeg -i input.mp4 -framerate 25 output.mjpeg"Getting all the individual images of my video (which worked fine) and put them together to a .mjpeg file did not work as well.
"ffmpeg -i input.mp4 image%d.jpeg"
"ffmpeg -f image2 -i image%d.jpeg output.mjpeg", or
"ffmpeg -f image2 -i image%d.jpeg -framerate 25 output.mjpeg""Solutions" like the following one did not work, cause I need a file extension .mjpeg so -c:v mjpeg is not enough cause I end up with sth. like .mov !
"ffmpeg -i input.mov -c:v mjpeg -q:v 3 -huffman optimal -an output.mov"To view my files I use vlc player.
I always end up with a .mjpeg file which has the length of 10 seconds and only shows the very first image of my 4000 pictures.
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subprocess.py returns a File Not Found error
7 avril 2021, par wasneeplusAs part of a video analysis script I wanted to find the duration of a video file. For this I found the script offered in the first answer to this question : How to get the duration of a video in Python ?


import subprocess

def get_length(filename):
 result = subprocess.run(["ffprobe", "-v", "error", "-show_entries",
 "format=duration", "-of",
 "default=noprint_wrappers=1:nokey=1", filename],
 stdout=subprocess.PIPE,
 stderr=subprocess.STDOUT)
 return float(result.stdout)


This code works fine when my friend runs it in a Jupyter server environment, but when I try it on my laptop the trouble starts.


When I imput the following filename into the function :


filename = "C:\\Users\\benja\\OneDrive - De Haagse Hogeschool\\Onderzoeken 3\\8V.mp4"


I get the following error :


Traceback (most recent call last):
 File "c:/Users/benja/OneDrive - De Haagse Hogeschool/Onderzoeken 3/python_script.py", line 9, in <module>
 num_of_frames = math.floor((pf.get_length(filename) - 1)) * 30
 File "c:\Users\benja\OneDrive - De Haagse Hogeschool\Onderzoeken 3\python_funcs.py", line 21, in get_length
 stderr=subprocess.STDOUT)
 File "C:\Users\benja\Anaconda3\lib\subprocess.py", line 466, in run
 with Popen(*popenargs, **kwargs) as process:
 File "C:\Users\benja\Anaconda3\lib\subprocess.py", line 769, in __init__
 restore_signals, start_new_session)
 File "C:\Users\benja\Anaconda3\lib\subprocess.py", line 1172, in _execute_child
 startupinfo)
FileNotFoundError: [WinError 2] Het systeem kan het opgegeven bestand niet vinden
</module>

I do realise that my problem is almost identical to that of several other questions on here. However, their solutions don't seem to work for me. I have tried to :


- 

- Add the location of ffmpeg-win64-4.2.2.exe to the Path system variable.
- Add the location of python.exe to the ComSpec system variable.
- Put the videofile in the same directory as the script.








I would be most grateful if someone could point me in the right direction. Thank you in advance.


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Hardware accelerated decoding with FFmpeg falls back to software decoding
9 février 2024, par iexavSo I have followed the FFmpeg example for hardware accelerated decoding exactly as it is (I am referring to this example).


https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/hw_decode.c#L76


But I still seem to be decoding with the software decoder. When I open the task manager on windows the GPU isn't getting used. Before I make a call to av_hwframe_transfer_data() I check whether the frame is in the relevant hw_pix_fmt format and it is. Everything works, no errors, nothing, except the GPU is doing nothing. Now as an example I tried decoding a video that uses vp9 as a codec. If I specify the hardware accelerated codec I want by name it actually does work.


vidCodec=avcodec_find_decoder_by_name("vp9_cuvid"); 


When I do this and look at the task manager I can see that the CPU does much less work and my GPU actually does Video Decode work. Having to specify the hardware accelerated decoder for every single video I am decoding is ridiculous though.


Edit : as per user4581301's answer, here are the pieces of relevant code. (It's actually in java because I am using the java FFmpeg wrapper but it's basically just making a bunch of calls to FFmpeg functions.)



 ArrayList<string> deviceTypes = new ArrayList<>();
 int type = AV_HWDEVICE_TYPE_NONE;
 while ((type = av_hwdevice_iterate_types(type)) != AV_HWDEVICE_TYPE_NONE) {
 BytePointer p = av_hwdevice_get_type_name(type);

 deviceTypes.add(CString(p));
 }
 boolean flag=false;

 for(int j=0;j* Allocate a codec context for the decoder */
 if ((video_c = avcodec_alloc_context3(vidCodec)) == null) {
 throw new Exception("avcodec_alloc_context3() error: Could not allocate video decoding context.");
 }


 /* copy the stream parameters from the muxer */

 if ((ret = avcodec_parameters_to_context(video_c, video_st.codecpar())) < 0) {
 releaseUnsafe();
 throw new Exception("avcodec_parameters_to_context() error " + ret + ": Could not copy the video stream parameters.");
 }
 

 video_c.get_format(AvFormatGetter.getInstance());
 AVBufferRef hardwareDeviceContext =av_hwdevice_ctx_alloc(type);

 if ((ret = av_hwdevice_ctx_create(hardwareDeviceContext, type,(String) null, null, 0)) < 0) {
 System.err.println("Failed to create specified HW device. error " + ret);

 }else{
 video_c.hw_device_ctx(av_buffer_ref(hardwareDeviceContext));

 }
 


 
//The function that gets called for get_format
@Override
 public int call(AVCodecContext context, IntPointer format) {
 int p;


 for (int i=0;;i++) {
 if ((p=format.get(i)) == hw_pix_fmt) {
 return p;
 }
 if(p==-1){
 break;
 }
 }

 System.out.println(hw_pix_fmt +" is not found in the codec context");
 // Error

 return AV_PIX_FMT_NONE;
 }
 
//The method that's used for decoding video frames
 public Optional<boolean> decodeVideoFrame(AVPacket pkt, boolean readPacket, boolean keyFrames) throws Exception {

 int ret;
 // Decode video frame
 if (readPacket) {
 ret = avcodec_send_packet(video_c, pkt);
 
 if (ret < 0) {
 System.out.println("error during decoding");
 return Optional.empty();
 }

 if (pkt.data() == null && pkt.size() == 0) {
 pkt.stream_index(-1);
 }
 
 }

 // Did we get a video frame?
 while (true) {
 ret = avcodec_receive_frame(video_c, picture_hw);

 if (ret == AVERROR_EAGAIN() || ret == AVERROR_EOF()) {
 if (pkt.data() == null && pkt.size() == 0) {
 return Optional.empty();
 } else {

 return Optional.of(true);

 }
 } else if (ret < 0) {

 // Ignore errors to emulate the behavior of the old API
 // throw new Exception("avcodec_receive_frame() error " + ret + ": Error during video decoding.");
 return Optional.of(true);

 }

 if (!keyFrames || picture.pict_type() == AV_PICTURE_TYPE_I) {
 
 if(picture_hw.format()==hw_pix_fmt){
 if (av_hwframe_transfer_data(
 picture, // The frame that will contain the usable data.
 picture_hw, // Frame returned by avcodec_receive_frame()
 0) < 0) {
 throw new Exception("Could not transfer data from gpu to cpu. ");

 }
 }
 //... The rest of the method here
 return Optional.of(false);

 }
 }
 }
</boolean></string>

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