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Six Best Amplitude Alternatives
10 décembre 2024, par Daniel Crough -
FFMPEG stereo track stops capturing at random times during a capture session
26 mai 2022, par mrwassenI am currently working on building a workflow to capture and archive a large stash of family and friends PAL and NTSC VHS tapes. The hardware setup is as follows :


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- JVC HR-7860S VCR
- s-video / RCA audio >
- ADVC-3000 converter
- SDI / BNC cable >
- Blackmagic Decklink Mini Recorder 4K PCIe card
- installed in a fairly hi-spec windows machine : AMD Ryzen 9 5900X 3.7 Ghz base 12 core, GEFORCE RTX 3060 12 gB, 32 gB ram














The plan is to capture to lossless AVI, then drop into an NLE (Vegas Pro v.16) to do a minimal amount of cleanup / trimming, then render to a more compressed video format (TBD) for upload to AWS S3 accessible through a family website.


The issue I am having is that when I run the capture using ffmpeg/directshow e.g. for a perfectly fine 90 min. PAL tape, at some random point of time during the capture one of the 2 stereo channels just stops capturing. This has happened with all of the tapes I have tested so far, and it happens at different times during the same video. I have examined the frames surrounding points in time when this happens, and it doesn't correlate to any transitions or jitter, but often just randomly in the middle of a perfectly smooth scene. Once the one channel stops capturing it never starts back up again during that capture session.


The ADVC-3000 and the VCR are both showing both stereo channels playing normally throughout the capture. The windows machine running the capture hardly breaks a sweat at any time, and the transfer easily keeps up constantly showing a speed = 1x which I assume means nothing lagging. Also there are no video/audio sync issues at any point in time even towards the end of long tapes e.g. 90 mins.


I am fairly new at ffmpeg, so I have spent extensive amounts of time reading up on forum posts and experimenting and have ended up with the following syntax :


ffmpeg -y -f dshow -rtbufsize 2000M -i video="Blackmagic WDM Capture":audio="Blackmagic WDM Capture" -codec:v v210 -pix_fmt yuv422p -codec:a pcm_s16le -b:a 128k -t 02:00:00 -r 25 -threads 4 -maxrate 2500k -filter:a "volume=1.5" output_v210_audio.avi



The capture runs without a single dropped frame, the only error I am getting when launching (and perhaps this is a smoking gun ?) is :




"Non-monotonous DTS in output stream 0:1 ; previous : 0, current : -30 ;
changing to 1. This may result in incorrect timestamps in the output
file."




I have tried to troubleshoot this in the hopes that it is tied to my issue but so far without luck.


Hoping somebody can help correct or modify my command line or perhaps other ideas to help resolve the issue.


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ValueError : I/O operation on closed file with ffmpeg
22 mars 2018, par AstroCodaI’m trying to get this (minimal working example) code to compile in a virtual environment on Anaconda which I’ve set up in a supercomputing cluster :
import numpy as np
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.animation as manimation
FFMpegWriter = manimation.writers['ffmpeg']
metadata = dict(title='Movie Test', artist='Matplotlib',
comment='Movie support!')
writer = FFMpegWriter(fps=15, metadata=metadata)
fig = plt.figure()
l, = plt.plot([], [], 'k-o')
plt.xlim(-5, 5)
plt.ylim(-5, 5)
x0, y0 = 0, 0
with writer.saving(fig, "writer_test.mp4", 100):
for i in range(100):
x0 += 0.1 * np.random.randn()
y0 += 0.1 * np.random.randn()
l.set_data(x0, y0)
writer.grab_frame()The thing is, this code works absolutely fine on my local machine (MacOSX) - Anaconda distribution ; Python 2.7 ; same matplotlib and numpy version, and I have ffmpeg on Anaconda ; I have ffmpeg on the cluster as well, albeit at a different version to the one on Python (but no issue with this on my local machine). When I run the code on the cluster, I get :
Traceback (most recent call last):
File "movie_test.py", line 25, in <module>
writer.grab_frame()
File "~/anaconda2/envs/test_movie/lib/python2.7/contextlib.py", line 35, in __exit__
self.gen.throw(type, value, traceback)
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 241, in saving
self.finish()
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 367, in finish
self.cleanup()
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/matplotlib/animation.py", line 405, in cleanup
out, err = self._proc.communicate()
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 927, in communicate
stdout, stderr = self._communicate(input, endtime, timeout)
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1713, in _communicate
orig_timeout)
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1769, in _communicate_with_poll
register_and_append(self.stdout, select_POLLIN_POLLPRI)
File "~/anaconda2/envs/test_movie/lib/python2.7/site-packages/subprocess32.py", line 1748, in register_and_append
poller.register(file_obj.fileno(), eventmask)
ValueError: I/O operation on closed file
</module>All the searches I’ve made correspond to relatively simple text write in/out operations, but not for videos. Thanks in advance for the help !