Hi, I'd like to know if someone can reproduce this problem: Make a 6s video with audio: ffmpeg -f lavfi -i testsrc2=size=vga -f lavfi -i sine=1000 -t 6 -y video.mp4 The video plays correctly and has 6s of audio. Now mix the audio channels from two of these input videos: ffmpeg -i video.mp4 -i video.mp4 -lavfi "[0:a][1:a]amix=weights='1.0 0.1'" -y out.mp4 You can hear that the audio from the first input ends too early at 4s, and the audio from the second input has the correct length 6s. Tested with FFplay and VLC. Known workaround: add -c:v mpeg4 This is ticket 8489, but so far nobody did have a look at it. Michael C:\Users\mKoch\Desktop>c:\ffmpeg\ffmpeg -f lavfi -i testsrc2=size=vga -f lavfi - i sine=1000 -t 6 -y video.mp4 ffmpeg version git-2020-02-25-36451f9 Copyright (c) 2000-2020 the FFmpeg develop ers   built with gcc 9.2.1 (GCC) 20200122   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-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvd ec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf   libavutil      56. 42.100 / 56. 42.100   libavcodec     58. 73.102 / 58. 73.102   libavformat    58. 39.101 / 58. 39.101   libavdevice    58.  9.103 / 58.  9.103   libavfilter     7. 77.100 /  7. 77.100   libswscale      5.  6.100 /  5.  6.100   libswresample   3.  6.100 /  3.  6.100   libpostproc    55.  6.100 / 55.  6.100 Input #0, lavfi, from 'testsrc2=size=vga':   Duration: N/A, start: 0.000000, bitrate: N/A     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc Input #1, lavfi, from 'sine=1000':   Duration: N/A, start: 0.000000, bitrate: 705 kb/s     Stream #1:0: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s Stream mapping:   Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))   Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (native)) Press [q] to stop, [?] for help [libx264 @ 00000000001bee80] using SAR=1/1 [libx264 @ 00000000001bee80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 [libx264 @ 00000000001bee80] profile High, level 3.0, 4:2:0, 8-bit [libx264 @ 00000000001bee80] 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 'video.mp4':   Metadata:     encoder         : Lavf58.39.101     Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p(progressive) , 640x480 [SAR 1:1 DAR 4:3], q=-1--1, 25 fps, 12800 tbn, 25 tbc     Metadata:       encoder         : Lavc58.73.102 libx264     Side data:       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A     Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 69 k b/s     Metadata:       encoder         : Lavc58.73.102 aac frame=  103 fps=0.0 q=28.0 size=       0kB time=00:00:02.02 bitrate=   0.2kbits/ frame=  150 fps=128 q=-1.0 Lsize=     690kB time=00:00:06.01 bitrate= 940.0kbits /s speed=5.14x video:633kB audio:51kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.899108% [libx264 @ 00000000001bee80] frame I:1     Avg QP:21.21  size:  9168 [libx264 @ 00000000001bee80] frame P:46    Avg QP:26.76  size:  5209 [libx264 @ 00000000001bee80] frame B:103   Avg QP:30.60  size:  3875 [libx264 @ 00000000001bee80] consecutive B-frames:  1.3% 10.7% 32.0% 56.0% [libx264 @ 00000000001bee80] mb I  I16..4: 25.0% 62.2% 12.8% [libx264 @ 00000000001bee80] mb P  I16..4:  1.5%  6.0%  1.0% P16..4:  9.3%  5.3 %  2.9%  0.0%  0.0%    skip:74.1% [libx264 @ 00000000001bee80] mb B  I16..4:  0.2%  0.4%  0.5% B16..8: 13.8%  4.2 %  1.0%  direct: 1.7%  skip:78.3%  L0:50.3% L1:42.7% BI: 7.0% [libx264 @ 00000000001bee80] 8x8 transform intra:63.2% inter:22.1% [libx264 @ 00000000001bee80] coded y,uvDC,uvAC intra: 16.1% 23.3% 22.4% inter: 4 .2% 8.7% 7.4% [libx264 @ 00000000001bee80] i16 v,h,dc,p: 70% 23%  6%  1% [libx264 @ 00000000001bee80] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 15% 73%  0%  0%  0%  0%  0%  0% [libx264 @ 00000000001bee80] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 22% 31%  6%  3%  4%  3%  5%  3% [libx264 @ 00000000001bee80] i8c dc,h,v,p: 69% 11% 19%  1% [libx264 @ 00000000001bee80] Weighted P-Frames: Y:0.0% UV:0.0% [libx264 @ 00000000001bee80] ref P L0: 55.3%  6.9% 23.3% 14.5% [libx264 @ 00000000001bee80] ref B L0: 71.5% 23.5%  5.0% [libx264 @ 00000000001bee80] ref B L1: 93.0%  7.0% [libx264 @ 00000000001bee80] kb/s:863.86 [aac @ 00000000032a88c0] Qavg: 19623.219 C:\Users\mKoch\Desktop>c:\ffmpeg\ffmpeg -i video.mp4 -i video.mp4 -lavfi "[0:a][ 1:a]amix=weights='1.0 0.1'" -y out.mp4 ffmpeg version git-2020-02-25-36451f9 Copyright (c) 2000-2020 the FFmpeg develop ers   built with gcc 9.2.1 (GCC) 20200122   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-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvd ec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf   libavutil      56. 42.100 / 56. 42.100   libavcodec     58. 73.102 / 58. 73.102   libavformat    58. 39.101 / 58. 39.101   libavdevice    58.  9.103 / 58.  9.103   libavfilter     7. 77.100 /  7. 77.100   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         : Lavf58.39.101   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 Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':   Metadata:     major_brand     : isom     minor_version   : 512     compatible_brands: isomiso2avc1mp41     encoder         : Lavf58.39.101   Duration: 00:00:06.02, start: 0.000000, bitrate: 938 kb/s     Stream #1:0(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 #1:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp,  68 kb/s (default)     Metadata:       handler_name    : SoundHandler Stream mapping:   Stream #0:1 (aac) -> amix:input0 (graph 0)   Stream #1:1 (aac) -> 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 @ 00000000004de280] using SAR=1/1 [libx264 @ 00000000004de280] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 [libx264 @ 00000000004de280] profile High, level 3.0, 4:2:0, 8-bit [libx264 @ 00000000004de280] 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         : Lavf58.39.101     Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 69 k b/s (default)     Metadata:       encoder         : Lavc58.73.102 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         : Lavc58.73.102 libx264     Side data:       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A frame=   95 fps=0.0 q=28.0 size=       0kB time=00:00:01.69 bitrate=   0.2kbits/ frame=  150 fps=130 q=-1.0 Lsize=     661kB time=00:00:06.01 bitrate= 900.9kbits /s speed=5.21x video:612kB audio:43kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.942758% [aac @ 0000000002990a40] Qavg: 25713.752 [libx264 @ 00000000004de280] frame I:1     Avg QP:18.28  size:  9171 [libx264 @ 00000000004de280] frame P:47    Avg QP:25.28  size:  5109 [libx264 @ 00000000004de280] frame B:102   Avg QP:29.85  size:  3690 [libx264 @ 00000000004de280] consecutive B-frames:  2.0% 13.3% 26.0% 58.7% [libx264 @ 00000000004de280] mb I  I16..4: 45.2% 42.3% 12.5% [libx264 @ 00000000004de280] 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 @ 00000000004de280] 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 @ 00000000004de280] 8x8 transform intra:56.4% inter:25.6% [libx264 @ 00000000004de280] coded y,uvDC,uvAC intra: 19.1% 27.7% 26.1% inter: 4 .0% 9.1% 7.5% [libx264 @ 00000000004de280] i16 v,h,dc,p: 71% 19%  8%  1% [libx264 @ 00000000004de280] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 12% 75%  0%  0%  0%  0%  0%  0% [libx264 @ 00000000004de280] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 18% 22% 33%  7%  3%  4%  4%  6%  4% [libx264 @ 00000000004de280] i8c dc,h,v,p: 71% 11% 17%  2% [libx264 @ 00000000004de280] Weighted P-Frames: Y:0.0% UV:0.0% [libx264 @ 00000000004de280] ref P L0: 56.9%  7.7% 22.6% 12.9% [libx264 @ 00000000004de280] ref B L0: 74.2% 21.4%  4.4% [libx264 @ 00000000004de280] ref B L1: 94.6%  5.4% [libx264 @ 00000000004de280] kb/s:834.26