Recherche avancée

Sur d’autres sites (14964)

• FFmpeg max audio overhead

  15 août 2020, par Alsors

  So I'm encoding videos with FFmpeg. I've set the video stream to have a maximum rate of 6840 kbps and the audio stream to have a constant rate of 160 kbps (AAC) so once they're added together it's a maximum combined rate of 7000 kbps (the maximum rate before my video sharing service re-encodes the video and audio). The problem is sometimes the audio stream likes to go above it's designated constant rate (not by much however enough to take it over 7000 kbps), even with the exact same command it'll sometimes go above and sometime stay the same.

  


  My question : is there a way to calculate the maximum overhead of the audio stream ? I'm assuming FFmpeg has a point where it will not allow the audio rate to go any higher ? What is that exact rate ?

  


• mp4 video written with ffmpeg has different first frame based on total number of frames

  25 janvier 2023, par Nitzan Weissman

  I have a code that writes and reads videos in Python, I'm doing the writing using ffmpeg. I noticed a weird phenomenon, where the first frame changes based on the total number of frames in the video. I find it weird because the first frame is a key frame (I checked it using ffprobe)

  


  The code I'm using :

  


  The writing function

  


  import shutil
import subprocess
def write_h264_video(video_path: str, images: np.ndarray, fps: float):
    image_name_template = '00%04d.png'
    tmp_image_dir = (Path(video_path).parent / 'tmp_imgs')
    tmp_image_dir.mkdir()

    for ii, image in enumerate(images):
        cv2.imwrite(f'{str(tmp_image_dir / str(ii).zfill(6))}.png', image[..., ::-1])    
    command = f'ffmpeg -hide_banner -loglevel error -framerate {fps} -y -i {tmp_image_dir}/{image_name_template} ' \
            f' -c:v libx264 -pix_fmt yuv420p {video_path} -y'
    subprocess.call(command, shell=True)
    shutil.rmtree(tmp_image_dir)


  


  The main code

  


  import numpy as np
from pathlib import Path
import decord
decord.bridge.set_bridge('torch')

input_video_path = Path('')
tmp_path = Path('')
input_video = decord.VideoReader(str(input_video_path))

frames = np.zeros((20, 512, 512, 3), dtype = np.uint8)
for i in range(20):
    frames[i] = input_video[i].detach().cpu().numpy()
    
long_video_path = tmp_path / 'long_video.mp4'
short_video_path = tmp_path / 'short_video.mp4'

fps = 30
write_h264_video(str(long_video_path), frames, fps=fps)
write_h264_video(str(short_video_path), frames[:10], fps=fps)


long_video = decord.VideoReader(str(long_video_path))
short_video = decord.VideoReader(str(short_video_path))

long_frame_0 = long_video[0]
short_frame_0 = short_video[0]
(long_frame_0 == short_frame_0).all()


  


  I am supposed to get True, but I'm getting False.
I tried reading using other methods, using opencv for example, and the issue persists.
There are other ways to write videos of course, but I'm interested in ffmpeg-based ways.

  


  Thanks !

  


• Dash JS Player Cross Browser Compatibility

  21 mai 2015, par JJ The Second

  I am conducting a research for my company streaming service. I found dash.js for adaptive streaming which is a perfect solution along with ffMpeg for transcoding.

  So how this solution works is to create bunch of files served in .mpd format. Now the questions I have :

  1. Do you think this a early stage and I should wait before start using DASH.JS ? Do you think there is a better solution for safe and fast streaming ?

  2. Player options : So far the only player I found was this http://dashif.org/reference/players/javascript/1.0.0/

     I have no idea how compatible it is with browsers and what limits I’ll be facing if I chose it. Is there any other solid solution for this ?

  3. Do you guys think I’m going wrong direction for this ?

  4. What are my server requirements to run these technologies ? I have a 500MBs, 64GB Ram, 24 Core, 2TB beast, does this do the job ?