>Have you tried adding (silent) audio to video 2 and trying your join
operation again? You could use `anullsrc':
This is what I am trying to do, but wasn't able to accomplish the first step
which is adding a silent audio to my video using anullsrc.
I came up with the following command after doing some search and also based
on Michael's command sample:
Ffmpeg -i video.mp4 -f lavfi -i anullsrc=r=48000:cl=2 -c:v copy -c:a aac
-shortest output.mp4
At the end of the console output I get the following:
>>>
Press [q] to stop, [?] for help
[aac @ 0000023281941140] Unsupported channel layout "1 channels (FR)"
[aac @ 0000023281941140] Qavg: nan
Error initializing output stream 0:1 -- Error while opening encoder for
output stream #0:1 - maybe incorrect parameters such as bit_rate, rate,
width or height
Conversion failed!
<<<
Here is some additional data:
1 - The file I need to concatenate to already has audio and below are the
parameters. As I need to create the silent audio with similar parameters, I
used the same sample rate and number of channels (48000 and 2)
[STREAM]
index=1
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=LC
codec_type=audio
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=fltp
sample_rate=48000
channels=2
channel_layout=stereo
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/48000
start_pts=0
start_time=0.000000
duration_ts=624000
duration=13.000000
bit_rate=129137
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=611
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
TAG:language=und
TAG:handler_name=SoundHandler
TAG:vendor_id=[0][0][0][0]
[/STREAM]
The full console output of adding the audio is here:
ffmpeg -i trans_final_4_radial.mp4 -f lavfi -i anullsrc=r=48000:cl=2 -c:v
copy -c:a aac -shortest trans_final_4_radial_WithAudio.mp4
ffmpeg version 2021-03-14-git-1d61a31497-essentials_build-www.gyan.dev
Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 10.2.0 (Rev6, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static
--disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv
--enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib
--enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth
--enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265
--enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx
--enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab
--enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm
--enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc
--enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme
--enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame
--enable-libtheora --enable-libvo-amrwbenc --enable-libgsm
--enable-libopencore-amrnb --enable-libopus --enable-libspeex
--enable-libvorbis --enable-librubberband
libavutil 56. 68.100 / 56. 68.100
libavcodec 58.131.100 / 58.131.100
libavformat 58. 74.100 / 58. 74.100
libavdevice 58. 12.100 / 58. 12.100
libavfilter 7.109.100 / 7.109.100
libswscale 5. 8.100 / 5. 8.100
libswresample 3. 8.100 / 3. 8.100
libpostproc 55. 8.100 / 55. 8.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'trans_final_4_radial.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.74.100
Duration: 00:00:04.10, start: 0.000000, bitrate: 301 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
1920x1080 [SAR 1:1 DAR 16:9], 293 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc
(default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
Input #1, lavfi, from 'anullsrc=r=48000:cl=2':
Duration: N/A, start: 0.000000, bitrate: 384 kb/s
Stream #1:0: Audio: pcm_u8, 48000 Hz, 1 channels (FR), u8, 384 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #1:0 -> #0:1 (pcm_u8 (native) -> aac (native))
Press [q] to stop, [?] for help
[aac @ 0000023281941140] Unsupported channel layout "1 channels (FR)"
[aac @ 0000023281941140] Qavg: nan
Error initializing output stream 0:1 -- Error while opening encoder for
output stream #0:1 - maybe incorrect parameters such as bit_rate, rate,
width or height
Conversion failed!
-----Original Message-----
From: ffmpeg-user <ffmpeg-user-boun...@ffmpeg.org> On Behalf Of Rob Hallam
Sent: Tuesday, June 22, 2021 1:31 PM
To: FFmpeg user questions <ffmpeg-user@ffmpeg.org>
Subject: Re: [FFmpeg-user] Audio out of sync after video concatenation
On Tue, 22 Jun 2021 at 11:15, <ibur...@compuscience.com> wrote:
> Video 1 - 13 seconds with audio
> Video 2 - 4 seconds without audio (I generated this video using xfade
> transition Video 3 - 4 seconds with audio
>
> If I concatenate video 1 and 3 everything works fine; audio
> synchronization is correct from start to end. However, when I
> concatenate all 3 of them, the audio from video 3 starts playing a
> little bit before the end of video 2. As video 3 is a person talking,
> you clearly see that the audio doesn't match the mouth movements.
>
> Why is this happening and how can I fix it?
Have you tried adding (silent) audio to video 2 and trying your join
operation again? You could use `anullsrc':
https://ffmpeg.org/ffmpeg-filters.html#anullsrc
or make silent audio elsewhere and add to video 2 separately.
You may also want to look up the `-shortest' option if you don't know of it
already.
Cheers,
Rob
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