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• avcodec/cbs_av1 : add an option to select an operating point

  15 novembre 2020, par James Almer

  avcodec/cbs_av1 : add an option to select an operating point
  This implements the function drop_obu() as defined in Setion 6.2.1 from the
  
  spec.
  
  In a reading only scenario, units that belong to an operating point the
  
  caller doesn't want should not be parsed.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/cbs_av1.c
  • [DH] libavcodec/cbs_av1.h

• 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 !

  


• Revision d1cff2deb1 : Code cleanup in bitstream code. Lower case variable names, less code. Change-I

  9 avril 2013, par Dmitry Kovalev

  Changed Paths : Modify /vp9/encoder/vp9_bitstream.c Code cleanup in bitstream code. Lower case variable names, less code. Change-Id : I1abc8f592ad2343ab5c76fe2d16262741a4a894a