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• Artifacts in ffmpeg fifo, low fps, stream ends

  11 août 2020, par Ben Gardner

  I'm using a Raspberry Pi 3B and 4 for this, neither works.

  


  I'm trying to both pass my capture card's input (/dev/video0) through a fifo file so I can play it on the screen via omxplayer (1080p/30fps), and also grab frames of /dev/video0 out to a series of jpgs (1920x1080 right now, but I'd like it to be 640x480) so I can do analysis on it while it's being played. The input to the capture card is television via HDMI.

  


  This is the command I use to make the stream go to the fifo and jpgs.

  


  ffmpeg -y -f v4l2 -input_format mjpeg -framerate 30 -video_size 1920x1080 \
-thread_queue_size 16384 -i /dev/video0 -f alsa -ac 1 \
-thread_queue_size 16384 -i hw:CARD=U0x534d0x2109,DEV=0 \
-c:v copy -b:v 32000k -preset faster -x264opts keyint=50 \
-g 25 -pix_fmt yuvj422p -c:a aac -b:a 128k -codec:v copy -f tee \
-map 0:v -map 1:a "fifo.mkv|output_%3d.jpg"


  


  Here is my output, which gives me 30fps originally, sometimes dipping into 29-28 fps, and then skipping (both audio and video) and artifacts in the video after around 5-10 minutes with the severity eventually increasing until it stops :

  


  [mjpeg @ 0x1504490] EOI missing, emulating
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 27151.039849, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 1920x1080, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Guessed Channel Layout for Input Stream #1.0 : mono
Input #1, alsa, from 'hw:CARD=U0x534d0x2109,DEV=0':
  Duration: N/A, start: 1596773777.825328, bitrate: 1536 kb/s
    Stream #1:0: Audio: pcm_s16le, 96000 Hz, mono, s16, 1536 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (native))
Press [q] to stop, [?] for help
Output #0, tee, to 'fifo.mkv|output_%3d.jpg':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 1920x1080, q=2-31, 32000 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
    Stream #0:1: Audio: aac (LC), 96000 Hz, mono, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.35.100 aac
[alsa @ 0x1507300] Thread message queue blocking; consider raising the thread_queue_size option (current value: 16384)
[alsa @ 0x1507300] ALSA buffer xrun.time=00:13:55.89 bitrate=N/A speed=0.972x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:14:16.02 bitrate=N/A speed=0.974x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:14:27.25 bitrate=N/A speed=0.972x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:14:33.35 bitrate=N/A speed=0.97x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:14:44.71 bitrate=N/A speed=0.969x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:14:49.71 bitrate=N/A speed=0.97x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:01.51 bitrate=N/A speed=0.967x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:07.78 bitrate=N/A speed=0.969x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:14.27 bitrate=N/A speed=0.962x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:26.44 bitrate=N/A speed=0.96x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:32.40 bitrate=N/A speed=0.96x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:38.63 bitrate=N/A speed=0.963x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:45.60 bitrate=N/A speed=0.959x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:15:50.93 bitrate=N/A speed=0.957x
    Last message repeated 1 times
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:00.79 bitrate=N/A speed=0.951x
    Last message repeated 1 times
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:05.29 bitrate=N/A speed=0.949x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:07.19 bitrate=N/A speed=0.949x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:11.72 bitrate=N/A speed=0.945x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:16.02 bitrate=N/A speed=0.944x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:26.39 bitrate=N/A speed=0.953x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:30.22 bitrate=N/A speed=0.938x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:30.98 bitrate=N/A speed=0.937x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:37.66 bitrate=N/A speed=0.941x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:41.28 bitrate=N/A speed=0.935x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:42.95 bitrate=N/A speed=0.934x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:45.82 bitrate=N/A speed=0.933x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:46.76 bitrate=N/A speed=0.932x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:47.05 bitrate=N/A speed=0.931x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:50.74 bitrate=N/A speed=0.927x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:57.05 bitrate=N/A speed=0.927x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:16:58.91 bitrate=N/A speed=0.927x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:17:09.41 bitrate=N/A speed=0.92x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:17:12.04 bitrate=N/A speed=0.917x
[alsa @ 0x1507300] ALSA buffer xrun.time=00:17:12.61 bitrate=N/A speed=0.916x
Killed31579 fps= 28 q=-1.0 size=N/A time=00:17:32.56 bitrate=N/A speed=0.919x


  


  I also occasionally get this error :

  


  [tee @ 0x17001c0] Non-monotonous DTS in output stream 0:1; previous: 99251754, current: 99247503; changing to 99251755. This may result in incorrect timestamps in the output file.


  


  I'm assuming this has something to do with the audio getting routed to the jpg. I've tried [select=\'v\'] in front of the jpg, which doesn't change the behavior as well as [map=\'1\:a\'] in front of the mkv, which says [matroska @ 0xe446f0] Unknown option 'map'.

  


  I should also disclaim that I don't have much of an idea of what this command is doing compression-wise, I basically just copy/pasted that part.

  


  What edits do I need to make to get this into a fifo and series of jpgs at the same time ?

  


• Python and ffmpeg audio sync and screen recording issues

  9 août 2020, par odddollar

  I'm using ffmpeg and python to record my desktop screen. When the program is run, it starts recording, then when I press a key-combo it cuts off the last x amount of seconds and saves it then starts recording again ; similar to the "record that" functionality of windows game bar.

  


  I have it working so it records video just fine, but then I change the ffmpeg command to record audio from my desktop and I get an error saying ValueError: could not convert string to float: 'N/A' occurring when I try to calculate the length of the recorded video. It appears as though the recording isn't being stopped until after I try to calculate the video length, even though this exact same code works fine when not recording audio.

  


  Additionally, I also have an issue when recording audio in that the audio is a couple hundred milliseconds in front of the video. It's not a lot but it's enough to be noticeable.

  


  What I'm overall asking, is there a way I can modify the ffmpeg command to prevent the audio desync issues, and what might be causing the problems I'm getting when attempting to find the length of the video with audio ?

  


  import keyboard, signal
from os import remove
from os.path import isfile
from subprocess import Popen, getoutput
from datetime import datetime
import configparser

class Main:
    def __init__(self, save_location, framerate, duration):
        self.save_location = save_location
        self.framerate = int(framerate)
        self.duration = int(duration)
        self.working = self.save_location + '\\' + 'working.avi'
        self.start_recording()

    def start_recording(self):
        if isfile(self.working):
            remove(self.working)

        # start recording to working file at set framerate
        self.process = Popen(f'ffmpeg -thread_queue_size 578 -f gdigrab -video_size 1920x1080 -i desktop -f dshow -i audio="Stereo Mix (Realtek High Definition Audio)" -b:v 7M -minrate 4M -framerate {self.framerate} {self.working}')
        #self.process = Popen(f'ffmpeg -f gdigrab -framerate {self.framerate} -video_size 1920x1080 -i desktop -b:v 7M -minrate 2M {self.working}')

    def trim_video(self):
        # stop recording working file
        self.process.send_signal(signal.CTRL_C_EVENT)

        # call 'cause I have to
        getoutput(f"ffprobe -i {self.working}")

        # get length of working video
        length = getoutput(f'ffprobe -i {self.working} -show_entries format=duration -v quiet -of csv="p=0"')

        # get time before desired recording time
        start = float(length) - self.duration

        # get save location and title
        title = self.save_location+'\\'+self.get_time()+'.avi'

        # cut to last amount of desired time
        Popen(f"ffmpeg -ss {start} -i {self.working} -c copy -t {self.duration} {title}")
        getoutput(f"ffprobe -i {self.working}")

        self.start_recording()

    def get_time(self):
        now = datetime.now()
        return now.strftime("%Y_%m_%d#%H-%M-%S")


if __name__ == "__main__":
    config = configparser.ConfigParser()
    config.read("settings.ini")
    config = config["DEFAULT"]

    run = Main(config["savelocation"].replace("\\", "\\\\"), config["framerate"], config["recordlast"])
    keyboard.add_hotkey("ctrl+shift+alt+g", lambda:run.trim_video())

    while True:
        try:
            keyboard.wait()
        except KeyboardInterrupt:
            pass


  


  The contents of the settings.ini file are listed below

  


  [DEFAULT]
savelocation = C:\
framerate = 30
recordlast = 10


  


  In the code block, the first line with self.process = Popen is the one that records audio and has the issues, the second line (the commented out one below) is the one that works fine.

  


• avutil/channel_layout : add 22.2 layout

  11 juin 2020, par Jan Ekström

  avutil/channel_layout : add 22.2 layout
  Requires some extraneous top side and bottom front channels to be
  
  defined.
  According to STD-B59v2, the defined channel layout is :
  
   FL
  
   FR
  
   FC
  
   LFE1
  
   BL
  
   BR
  
   FLc
  
   FRc
  
   BC
  
   LFE2
  
   SiL
  
   SiR
  
   TpFL
  
   TpFR
  
   TpFC
  
   TpC
  
   TpBL
  
   TpBR
  
   TpSiL
  
   TpSiR
  
   TpBC
  
   BtFC
  
   BtFL
  
   BtFR
  

  • [DH] doc/APIchanges
  • [DH] libavutil/channel_layout.c
  • [DH] libavutil/channel_layout.h
  • [DH] libavutil/version.h