FFmpeg concat creating corrupted video part (Media Info provided)

Question

I am using concat to join a list of video files with the following command

ffmpeg -f concat -safe 0 -i filesList.txt -c copy output.mp4 

The issue here is that there are a few files that were recorded in slow motion on my phone. The slow-motion files have the same frame rate as the other files.

But when concatenated the part where the slow-motion files are concatenated appears to be frozen / glitch (it does not play a single frame).

I am able to seek forward and backward the part that does not play. So the portion of the video that contained normal files plays and as soon as the slow-motion video comes, nothing plays, and when a normal file comes it starts playing again.

I am attaching the media Info of both files

Info of the slow motion file:

General
Complete name :     I:\concate Test\VID20210727114100.mp4
Format :    MPEG-4
Format profile :    Base Media / Version 2
Codec ID :  mp42 (isom/mp42)
File size :     27.6 MiB
Duration :  1 min 0 s
Overall bit rate :  3 825 kb/s
Encoded date :  UTC 2021-07-27 06:11:08
Tagged date :   UTC 2021-07-27 06:11:08
xyz :   +21.6146+071.2342/
com.android.version :   11

Video
ID :    1
Format :    HEVC
Format/Info :   High Efficiency Video Coding
Format profile :    [email protected]@Main
Codec ID :  hvc1
Codec ID/Info :     High Efficiency Video Coding
Duration :  1 min 0 s
Source duration :   1 min 0 s
Bit rate :  3 771 kb/s
Width :     1 280 pixels
Height :    720 pixels
Display aspect ratio :  16:9
Frame rate mode :   Variable
Frame rate :    30.000 FPS
Minimum frame rate :    29.910 FPS
Maximum frame rate :    30.090 FPS
Real frame rate :   240.000 FPS
Color space :   YUV
Chroma subsampling :    4:2:0
Bit depth :     8 bits
Bits/(Pixel*Frame) :    0.136
Stream size :   27.2 MiB (99%)
Source stream size :    27.2 MiB (99%)
Title :     VideoHandle
Language :  English
Encoded date :  UTC 2021-07-27 06:11:08
Tagged date :   UTC 2021-07-27 06:11:08
Color range :   Limited
Color primaries :   BT.709
Transfer characteristics :  BT.709
Matrix coefficients :   BT.709
mdhd_Duration :     60524
Codec configuration box :   hvcC

Info of the regular video file

General
Complete name :     I:\concate Test\VID20210727113901.mp4
Format :    MPEG-4
Format profile :    Base Media / Version 2
Codec ID :  mp42 (isom/mp42)
File size :     39.0 MiB
Duration :  37 s 930 ms
Overall bit rate :  8 615 kb/s
Encoded date :  UTC 2021-07-27 06:09:40
Tagged date :   UTC 2021-07-27 06:09:40
xyz :   +21.6146+071.2342/
com.android.version :   11

Video
ID :    1
Format :    HEVC
Format/Info :   High Efficiency Video Coding
Format profile :    Main@L4@Main
Codec ID :  hvc1
Codec ID/Info :     High Efficiency Video Coding
Duration :  37 s 930 ms
Source duration :   37 s 900 ms
Bit rate :  8 408 kb/s
Width :     1 920 pixels
Height :    1 080 pixels
Display aspect ratio :  16:9
Frame rate mode :   Variable
Frame rate :    29.604 FPS
Minimum frame rate :    29.508 FPS
Maximum frame rate :    29.605 FPS
Real frame rate :   30.000 FPS
Color space :   YUV
Chroma subsampling :    4:2:0
Bit depth :     8 bits
Bits/(Pixel*Frame) :    0.137
Stream size :   38.0 MiB (98%)
Source stream size :    38.0 MiB (98%)
Title :     VideoHandle
Language :  English
Encoded date :  UTC 2021-07-27 06:09:40
Tagged date :   UTC 2021-07-27 06:09:40
Color range :   Limited
Color primaries :   BT.709
Transfer characteristics :  BT.709
Matrix coefficients :   BT.709
mdhd_Duration :     37930
Codec configuration box :   hvcC

Audio
ID :    2
Format :    AAC LC
Format/Info :   Advanced Audio Codec Low Complexity
Codec ID :  mp4a-40-2
Duration :  37 s 909 ms
Bit rate mode :     Constant
Bit rate :  128 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 :   592 KiB (1%)
Title :     SoundHandle
Language :  English
Encoded date :  UTC 2021-07-27 06:09:40
Tagged date :   UTC 2021-07-27 06:09:40

Answer 1

Yes, resolution is the problem.

Try something like:

ffmpeg -i file1.mp4 -i files2 \
  -vsync vfr
  -filter "[0:v][1:v]scale2ref[vout0][vout1];\
           [vout0][0:a][vout1][1:a]concat=n=2:v=2:a=2[vout][aout]" \
  -map [vout] -map [aout] output.mp4 

scale2ref filter scales the 1st input to match the other. So, flip both its input and outputs if you want to scale the other way.

And no, you cannot copy, you must reencode.