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• FFMPEG distorting when resampling audio

  19 août 2017, par jsamaudio

  I’m making an mp3 from a flac file with ffmpeg. This is usually hum-dum for me.

  Tonight, for some reason, the converted audio is distorting when I use the same commands I’ve always used. After troubleshooting, it appears the problem is the "-out_sample_rate" flag.

  My command :

  ffmpeg -i input.flac -write_id3v1 1 -id3v2_version 3 -dither_method modified_e_weighted -out_sample_rate 44.1k -b:a 320k output.mp3

  The audio in the mp3 is then incredibly distorted by a jacked gain resulting in digital clipping.

  I’ve tried updating ffmpeg, and then problem remains. I’ve tried converting various sample rates (44.1k source files, 48k source files, 96k source files) to both 44.1k and 48k mp3s, problem remains whenever there’s a conversion.

  I’m on macOS, and I installed ffmpeg via homebrew.

  Any ideas ?

• Input/output error while using ffmpeg with pulse

  2 septembre 2017, par user116522

  i want to record my audio output. Yesterday, i used the following command

  ffmpeg -f pulse -ac 2 -i 1 -c:a libfdk_aac -b:a 192k test4.m4a

  and it was working. But now, i receive the output :

   ffmpeg version N-83415-g012dd8c Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 4.8 (SUSE Linux)
  
    configuration: --enable-gpl --enable-libx264 --enable-libx265 --enable-nonfree --enable-libfdk-aac --enable-libpulse
  
    libavutil      55. 46.100 / 55. 46.100
  
    libavcodec     57. 75.100 / 57. 75.100
  
    libavformat    57. 66.101 / 57. 66.101
  
    libavdevice    57.  2.100 / 57.  2.100
  
    libavfilter     6. 73.100 /  6. 73.100
  
    libswscale      4.  3.101 /  4.  3.101
  
    libswresample   2.  4.100 /  2.  4.100
  
    libpostproc    54.  2.100 / 54.  2.100
  
  1: Input/output error

  The command

  pactl list sources

  says :

  Source #0
  
          State: SUSPENDED
  
          Name: alsa_output.pci-0000_01_00.1.hdmi-stereo.monitor
  
          Description: Monitor of HDA NVidia Digital Stereo (HDMI)
  
          Driver: module-alsa-card.c
  
          Sample Specification: s16le 2ch 44100Hz
  
          Channel Map: front-left,front-right
  
          Owner Module: 6
  
          Mute: no
  
          Volume: front-left: 65536 / 100% / 0,00 dB,   front-right: 65536 / 100% / 0,00 dB
  
                  balance 0,00
  
          Base Volume: 65536 / 100% / 0,00 dB
  
          Monitor of Sink: alsa_output.pci-0000_01_00.1.hdmi-stereo
  
          Latency: 0 usec, configured 0 usec
  
          Flags: DECIBEL_VOLUME LATENCY 
  
          Properties:
  
                  device.description = "Monitor of HDA NVidia Digital Stereo (HDMI)"
  
                  device.class = "monitor"
  
                  alsa.card = "1"
  
                  alsa.card_name = "HDA NVidia"
  
                  alsa.long_card_name = "HDA NVidia at 0xf7080000 irq 17"
  
                  alsa.driver_name = "snd_hda_intel"
  
                  device.bus_path = "pci-0000:01:00.1"
  
                  sysfs.path = "/devices/pci0000:00/0000:00:01.0/0000:01:00.1/sound/card1"
  
                  device.bus = "pci"
  
                  device.vendor.id = "10de"
  
                  device.vendor.name = "NVIDIA Corporation"
  
                  device.product.id = "0fb9"
  
                  device.string = "1"
  
                  module-udev-detect.discovered = "1"
  
                  device.icon_name = "audio-card-pci"
  
          Formats:
  
                  pcm

• How to identify users in video file when streaming video ? [on hold]

  24 octobre 2017, par blackjak231

  I’m trying to find a solution to "secure" online video courses on a video streaming platform. The goals are the following :

  • Prevent easy download of video - OK
  • Be able to identify which connected user downloaded the video if it happens - NOK

  The server will be a Debian machine running PHP 7 and the "encryption" of the video will be done "on the stream" for each user.

  ---

  My question is for the second point. I’m unable to find a good solution for it. Here is what i thought of so far and the downsides :

  1. Add a watermark with the user’s name/email with "ffmpeg" on the whole video (in a corner)
     • Can be blurred and therefore useless
  2. Add an invisible digital watermark (inside the video file) with a tool (which i have not found yet)
     • Screen can be recorded and the invisible digital watermark lost.
  3. Add a watermark with the user’s name/email on 2 or 3 specific frames of the video while streaming using "ffmpeg"
     • Best solution from my point of view but no technical solution found so far.

  ---

  Do you have any recommendations on how to do this or a completely different approach to the problem ?

  I’m open to any third party video tool such as Vimeo or any other available.

  Thank you in advance for your help ! :)