How do I use ffmpeg to concatenate 2 videos and add a period of silence + black screen between them?

Question

There are several existing examples, but I'd like a single command that uses complex_filter to achieve the objective without doing extra things like generating blank video / audio files.

Looking around, this is the best I've come up with so far:

ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "color=black:s=960x540:d=1[b0];aevalsrc=0:d=1[s0];[0:v:0][0:a:0][b0][s0][1:v:0][1:a:0]concat=n=3:v=1:a=1[outv][outa]" -map '[outv]' -map '[outa]' out.mp4

My understanding of the breakdown of such a command is

1. specify 2 inputs
2. define a complex filter
3. define a black video stream of duration 1s and call it b0
4. define a silent audio stream of duration 1s and call it s0
5. pipe it through the concat filter with

• First stream: [0:v:0][0:a:0] // video1.mp4
• Second stream: [b0][s0] // stuff I defined earlier
• Third stream: [1:v:0][1:a:0] // video2.mp4

6. define 2 output streams [outv][outa] for video and audio respectively
7. combine them into out.mp4

All file inputs are correctly 960x540, all using the same audio and video codecs but ffmpeg gives me this error and starts using 100% CPU

More than 1000 frames duplicated

I think there's something wrong with the streams I'm defining in the filter - what's wrong? Do I need to specify more parameters somewhere?

EDIT: Here's a MediaInfo printout of the input video's metadata

Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/mp41)
File size                                : 7.82 MiB
Duration                                 : 31 s 449 ms
Overall bit rate                         : 2 086 kb/s
Writing application                      : Lavf59.16.100

Video
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main@L3@Main
Codec ID                                 : hvc1
Codec ID/Info                            : High Efficiency Video Coding
Duration                                 : 31 s 449 ms
Bit rate                                 : 1 973 kb/s
Maximum bit rate                         : 2 000 kb/s
Width                                    : 960 pixels
Height                                   : 540 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 0)
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.159
Stream size                              : 7.40 MiB (95%)
Writing library                          : x265 3.4+31-6722fce1f:[Mac OS X][clang 12.0.0][64 bit] 8bit+10bit+12bit
Encoding settings                        : cpuid=1111039 / frame-threads=4 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=960x540 / interlace=0 / total-frames=0 / level-idc=0 / high-tier=1 / uhd-bd=0 / ref=3 / no-allow-non-conformance / no-repeat-headers / annexb / no-aud / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=23 / keyint=250 / gop-lookahead=0 / bframes=4 / b-adapt=2 / b-pyramid / bframe-bias=0 / rc-lookahead=20 / lookahead-slices=0 / scenecut=40 / hist-scenecut=0 / radl=0 / no-splice / no-intra-refresh / ctu=64 / min-cu-size=8 / no-rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=0 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / strong-intra-smoothing / max-merge=3 / limit-refs=1 / no-limit-modes / me=1 / subme=2 / merange=57 / temporal-mvp / no-frame-dup / no-hme / weightp / no-weightb / no-analyze-src-pics / deblock=0:0 / sao / no-sao-non-deblock / rd=3 / selective-sao=4 / early-skip / rskip / no-fast-intra / no-tskip-fast / no-cu-lossless / b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=0.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=abr / bitrate=2000 / qcomp=0.60 / qpstep=4 / stats-write=1 / stats-read=0 / slow-firstpass / ipratio=1.40 / pbratio=1.30 / aq-mode=2 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=1 / overscan=0 / videoformat=5 / range=0 / colorprim=1 / transfer=1 / colormatrix=1 / chromaloc=1 / chromaloc-top=0 / chromaloc-bottom=0 / display-window=0 / cll=0,0 / min-luma=0 / max-luma=255 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / hist-threshold=0.03 / no-opt-cu-delta-qp / no-aq-motion / no-hdr10 / no-hdr10-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=0 / analysis-save-reuse-level=0 / analysis-load-reuse-level=0 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=1 / refine-ctu-distortion=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-analysis-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei / no-hevc-aq / no-svt / no-field / qp-adaptation-range=1.00 / scenecut-aware-qp=0conformance-window-offsets / right=0 / bottom=0 / decoder-max-rate=0 / no-vbv-live-multi-pass
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : hvcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 31 s 449 ms
Source duration                          : 31 s 492 ms
Source_Duration_LastFrame                : -17 ms
Bit rate mode                            : Constant
Bit rate                                 : 106 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 405 KiB (5%)
Source stream size                       : 406 KiB (5%)
Title                                    : Core Media Audio
Language                                 : English
Default                                  : Yes
Alternate group                          : 1

Answer 1

The warning/error

More than 1000 frames duplicated

produced by concat filter occurs as @Gyan eloquently put it in the comment under OP:

This usually happens when the videos are VFR or inputs have different frame rates or frame rate can't be ascertained by the concat filter.

So, make sure the framerates of all video streams including the filler streams created by the input filters. The same applies to the audio streams.

So try

ffmpeg -i video1.mp4 -i video2.mp4 \
  -filter_complex "color=black:s=960x540:d=1[b0]:r=24000/1001;\
                   aevalsrc=0:s=44100:d=1[s0];\
                   [0:v:0][0:a:0][b0][s0][1:v:0][1:a:0]concat=n=3:v=1:a=1[outv][outa]" \
  -map '[outv]' -map '[outa]' out.mp4

Note that aevalsrc's default sampling rate is 44100. So s=44100 is not required but is a good reminder of this matching requirement.