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• ffmpeg How to get PCM floats from AVFrame with AV_SAMPLE_FMT_FLT

  26 novembre 2020, par cs guy

  I have an AVFrame obtained through a decoder that has a format of AVSampleFormat::AV_SAMPLE_FMT_FLT. My issue is I want to convert the data stored inside

  


  avFrame->data; // returns uint8_t *


  


  to Array of floats that are between [-1, +1]. I see that avFrame->data; returns uint8_t * how may I use this to obtain the float pcm data for each channel of the audio ?

  


  I tried the following :

  


  auto *floatArrPtr = (float *)(avResampledDecFrame->data[0]);

    for (int i = 0; i < avResampledDecFrame->nb_samples; i++) {
        // TODO: store interleaved floats somewhere
        floatArrPtr++;
    }


  


  but I am not sure if this is the right way to get data

  


• How to create a video out of frames without saving it to disk using python ?

  6 septembre 2022, par brenodacosta

  I have a function that returns a frame as result. I wanted to know how to make a video out of a for-loop with this function without saving every frame and then creating the video.

  


  What I have from now is something similar to :

  


  import cv2
out = cv2.VideoWriter('video.mp4',cv2.VideoWriter_fourcc(*'DIVX'), 14.25,(500,258))
for frame in frames:
    img_result = MyImageTreatmentFunction(frame) # returns a numpy array image
    out.write(img_result)
out.release()


  


  Then the video will be created as video.mp4 and I can access it on memory. I'm asking myself if there's a way to have this video in a variable that I can easily convert to bytes later. My purpose for that is to send the video via HTTP post.

  


  I've looked on ffmpeg-python and opencv but I didn't find anything that applies to my case.

  


• Monitoring ffmpeg two-passes encoding

  31 décembre 2024, par Hodol

  I'm new in FFMPEG.

  


  According to the official guide, https://trac.ffmpeg.org/wiki/Encode/VP9 I use the following command to convert a large h.264 file :

  


  ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an -f null /dev/null
ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 -c:a libopus output.webm


  


  However, the pass-1 takes too long time and it does not log progress. With -report option I can see something is in progress but I don't know how long I should wait.

  


  Here's questions :

  


  

  1. Is there any way to see the progress of 1-pass ?

  


  2. Is there any way to speed up the process ?

  


  


  Thank you,