[FFmpeg-user] Screen capture is producing crackling noise

[Abeba Tensai]

Hi guys,

I am using a Mac (High Sierra 10.13.1).
Initially, I executed the following command to get the devices index:

> ffmpeg -f avfoundation  -list_devices true -i ""

ffmpeg version 3.3.5 Copyright (c) 2000-2017 the FFmpeg developers

  built with Apple LLVM version 9.0.0 (clang-900.0.39.2)

  configuration: --target-os=darwin --arch=x86_64 --enable-cross-compile
--disable-debug --enable-videotoolbox --disable-doc --enable-pic
--enable-protocol=https --enable-openssl --extra-cflags='-arch x86_64'
--extra-ldflags='-arch x86_64 -framework VideoToolbox' --disable-shared
--enable-static --pkg-config-flags=--static
--prefix=/Users/atensai/ffmpeg-3.3.5-x86_64

  libavutil      55. 58.100 / 55. 58.100

  libavcodec     57. 89.100 / 57. 89.100

  libavformat    57. 71.100 / 57. 71.100

  libavdevice    57.  6.100 / 57.  6.100

  libavfilter     6. 82.100 /  6. 82.100

  libswscale      4.  6.100 /  4.  6.100

  libswresample   2.  7.100 /  2.  7.100

[AVFoundation input device @ 0x7f89ff40d700] AVFoundation video devices:

[AVFoundation input device @ 0x7f89ff40d700] [0] FaceTime HD Camera

[AVFoundation input device @ 0x7f89ff40d700] [1] Capture screen 0

[AVFoundation input device @ 0x7f89ff40d700] AVFoundation audio devices:

[AVFoundation input device @ 0x7f89ff40d700] [0] Soundflower (64ch)

[AVFoundation input device @ 0x7f89ff40d700] [1] Built-in Microphone

[AVFoundation input device @ 0x7f89ff40d700] [2] Soundflower (2ch)

[AVFoundation input device @ 0x7f89ff40d700] [3] WavTap




Then I produced an audio capture (m4a) using the following command:
> ffmpeg -y -f avfoundation -i "1:2" -map 0:a -c:a aac_at -b:a 128k out.m4a
I get a file that sounds perfect

Then I tried to produce an audio/video file using the command:
> ffmpeg -y -f avfoundation -video_size 640x480  -pix_fmt yuyv422 -i "1:2"
-b:v 7500k -c:a aac -b:a 64k -vsync 2 -async 1 out.mp4
Everything looks good except that the audio has crackling noise which is
very pronounced when people are talking

Can someone help me with that?

Thanks.