[FFmpeg-user] Mix a video with an audio file

Sun Jan 19 21:26:49 EET 2020

Hello,

I've just found a problem that can be reproduced as follows:

Step 1: Make a 6 seconds test video with 1kHz tone. The file is ok when 
played.

ffmpeg -f lavfi -i testsrc2=size=vga -f lavfi -i sine=1000 -t 6 -y video.mp4

Step 2: Make a 10 seconds audio file with silence and a short 3kHz tone 
at t=3s. The file is ok when played.

ffmpeg -f lavfi -i "sine=3000:duration=0.1" -af adelay=3000,apad -t 10 
-y audio.wav

Step 3: Combine both files into one video, and the audio sources shall 
be mixed:

ffmpeg -i video.mp4 -i audio.wav -filter_complex 
"[0:a][1:a]amix=weights='1.0 1.0'" -shortest -y out.mp4

The output video has the correct length 6s, but I don't understand why 
the 1kHz tone disappears after 4s and the last 2s are silence.

The console output is below.

Michael

F:\Test_Audio>c:\ffmpeg\ffmpeg -i video.mp4 -i audio.wav -filter_complex 
"[0:a][
1:a]amix=weights='1.0 1.0'" -shortest -y out.mp4
ffmpeg version git-2020-01-15-0dc0837 Copyright (c) 2000-2020 the FFmpeg 
develop
ers
   built with gcc 9.2.1 (GCC) 20200111
   configuration: --enable-gpl --enable-version3 --enable-sdl2 
--enable-fontconfi
g --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d 
--enable-libb
luray --enable-libfreetype --enable-libmp3lame 
--enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus 
--enable-libshine --e
nable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame 
--enable
-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 
--enable-libx265 -
-enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib 
--enable-gmp --enab
le-libvidstab --enable-libvorbis --enable-libvo-amrwbenc 
--enable-libmysofa --en
able-libspeex --enable-libxvid --enable-libaom --enable-libmfx 
--enable-ffnvcode
c --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec 
--enable-dxva2 -
-enable-avisynth --enable-libopenmpt --enable-amf
   libavutil      56. 38.100 / 56. 38.100
   libavcodec     58. 65.103 / 58. 65.103
   libavformat    58. 35.102 / 58. 35.102
   libavdevice    58.  9.103 / 58.  9.103
   libavfilter     7. 71.100 /  7. 71.100
   libswscale      5.  6.100 /  5.  6.100
   libswresample   3.  6.100 /  3.  6.100
   libpostproc    55.  6.100 / 55.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     encoder         : Lavf58.35.102
   Duration: 00:00:06.02, start: 0.000000, bitrate: 938 kb/s
     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 
640x480 [
SAR 1:1 DAR 4:3], 864 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
     Metadata:
       handler_name    : VideoHandler
     Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 
mono, fltp,
  68 kb/s (default)
     Metadata:
       handler_name    : SoundHandler
Guessed Channel Layout for Input Stream #1.0 : mono
Input #1, wav, from 'audio.wav':
   Metadata:
     encoder         : Lavf58.35.102
   Duration: 00:00:10.00, bitrate: 705 kb/s
     Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 
mono, s16,
705 kb/s
Stream mapping:
   Stream #0:1 (aac) -> amix:input0 (graph 0)
   Stream #1:0 (pcm_s16le) -> amix:input1 (graph 0)
   amix (graph 0) -> Stream #0:0 (aac)
   Stream #0:0 -> #0:1 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 00000000029d7540] using SAR=1/1
[libx264 @ 00000000029d7540] using cpu capabilities: MMX2 SSE2Fast SSSE3 
SSE4.2
AVX FMA3 BMI2 AVX2
[libx264 @ 00000000029d7540] profile High, level 3.0, 4:2:0, 8-bit
[libx264 @ 00000000029d7540] 264 - core 159 - H.264/MPEG-4 AVC codec - 
Copyleft
2003-2019 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 
deblock=1
:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 
me_rang
e=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 
chroma_qp_
offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 
interla
ced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 
b_adapt=1 b_bias
=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 
scenecut=40
intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 
qpmin=0 qpma
x=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'out.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     encoder         : Lavf58.35.102
     Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, 
fltp, 69 k
b/s (default)
     Metadata:
       encoder         : Lavc58.65.103 aac
     Stream #0:1(und): Video: h264 (libx264) (avc1 / 0x31637661), 
yuv420p, 640x48
0 [SAR 1:1 DAR 4:3], q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
     Metadata:
       handler_name    : VideoHandler
       encoder         : Lavc58.65.103 libx264
     Side data:
       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame=  111 fps=0.0 q=28.0 size=     256kB time=00:00:02.36 bitrate= 
885.6kbits/
frame=  150 fps=141 q=-1.0 Lsize=     635kB time=00:00:06.01 bitrate= 
864.7kbits
/s speed=5.66x
video:612kB audio:17kB subtitle:0kB other streams:0kB global headers:0kB 
muxing
overhead: 0.982628%
[aac @ 00000000029dbb40] Qavg: 62202.113
[libx264 @ 00000000029d7540] frame I:1     Avg QP:18.28  size:  9171
[libx264 @ 00000000029d7540] frame P:47    Avg QP:25.28  size:  5109
[libx264 @ 00000000029d7540] frame B:102   Avg QP:29.85  size:  3690
[libx264 @ 00000000029d7540] consecutive B-frames:  2.0% 13.3% 26.0% 58.7%
[libx264 @ 00000000029d7540] mb I  I16..4: 45.2% 42.3% 12.5%
[libx264 @ 00000000029d7540] mb P  I16..4:  1.5%  5.5%  0.8% P16..4: 
11.1%  5.0
%  2.8%  0.0%  0.0%    skip:73.3%
[libx264 @ 00000000029d7540] mb B  I16..4:  0.2%  0.1%  0.5% B16..8: 
14.1%  3.7
%  0.9%  direct: 1.7%  skip:78.6%  L0:49.5% L1:44.3% BI: 6.2%
[libx264 @ 00000000029d7540] 8x8 transform intra:56.4% inter:25.6%
[libx264 @ 00000000029d7540] coded y,uvDC,uvAC intra: 19.1% 27.7% 26.1% 
inter: 4
.0% 9.1% 7.5%
[libx264 @ 00000000029d7540] i16 v,h,dc,p: 71% 19%  8%  1%
[libx264 @ 00000000029d7540] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 12% 75%  
0%  0%
  0%  0%  0%  0%
[libx264 @ 00000000029d7540] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 18% 22% 33%  
7%  3%
  4%  4%  6%  4%
[libx264 @ 00000000029d7540] i8c dc,h,v,p: 71% 11% 17%  2%
[libx264 @ 00000000029d7540] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 00000000029d7540] ref P L0: 56.9%  7.7% 22.6% 12.9%
[libx264 @ 00000000029d7540] ref B L0: 74.2% 21.4%  4.4%
[libx264 @ 00000000029d7540] ref B L1: 94.6%  5.4%
[libx264 @ 00000000029d7540] kb/s:834.26