Concat multiple (self-generated) videos using ffmpeg on raspbian linux - linux

Question

I am a very talented sleep talker, so I decided to write a solution that records the things I talk at night to make funny videos with subtitles of it. The project is nearly done, but I got a big problem with concating videos I generated before.
The video parts are generated from single png frames using this command:
ffmpeg -y -framerate 15 -i "${images_file_path}" -c:v libx264 -r 30 -pix_fmt yuv420p "${video_file_path}"
Then the sound is added using this command (got this from #9049970 and #11779490):
ffmpeg -y -i "${video_file_path}" -i "${mp3_file_path}" -map 0:v -map 1:a -vcodec copy -acodec copy -shortest "${final_video_file_path}"
All this is causing no problems so far, but I think it may be relevant to know how the videos are generated. I can watch all this and get valid video and sound - the full source code of this first part can be found here.
Now I added a feature that is able to generate "full videos" containing a title and a various number of previously generated "video parts" using this command:
ffmpeg -f concat -i "${video_list_path}" -filter_complex "${filter_string} concat=n=${input_file_counter}:v=1:a=1 [v] [a]" -map "[v]" -map "[a]" "${full_video_path}"
But something is wrong with it and I get this error:
Invalid file index 1 in filtergraph description [0:v:0] [1:v:0] [2:v:0] [2:a:0] [3:v:0] [4:v:0] [4:a:0] [5:v:0] [6:v:0] [6:a:0] [7:v:0] concat=n=8:v=1:a=1 [v] [a].
The full output is:
ffmpeg version N-77213-g7c1c453 Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.9.2 (Raspbian 4.9.2-10)
configuration: --enable-shared --enable-gpl --prefix=/usr --enable-nonfree --enable-libmp3lame --enable-libfaac --enable-libx264 --enable-version3 --disable-mmx
libavutil 55. 10.100 / 55. 10.100
libavcodec 57. 17.100 / 57. 17.100
libavformat 57. 20.100 / 57. 20.100
libavdevice 57. 0.100 / 57. 0.100
libavfilter 6. 20.100 / 6. 20.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
[mov,mp4,m4a,3gp,3g2,mj2 # 0xc2e900] Auto-inserting h264_mp4toannexb bitstream filter
Input #0, concat, from '/usr/sleeptalk/records-rendered/3enguzpuu2gw0ogk8wkko/videos.txt':
Duration: N/A, start: 0.000000, bitrate: 61 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 58 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 2 kb/s
Metadata:
handler_name : SoundHandler
Invalid file index 1 in filtergraph description [0:v:0] [1:v:0] [2:v:0] [2:a:0] [3:v:0] [4:v:0] [4:a:0] [5:v:0] [6:v:0] [6:a:0] [7:v:0] concat=n=8:v=1:a=1 [v] [a].
I also wrote a test case so you can reproduce this on your local machine. Download the files from my dropbox. Also, the full script that renders the "final move" can be found here.
Would be great to get an Idea, got struggle to fix this the last two days.

Answer 1

You're using both the concat demuxer as well as the concat filter. Skip the latter, because
a) it's unnecessary and
b) I don't believe the demuxer is inducting all input files as separate inputs so the indices beyond 0 don't make sense. Also, the concat filter needs equal number of streams per input file, and their input assignment has to be pair-wise i.e. [0:v:0] [0:a:0] [1:v:0] [1:a:0] [2:v:0] [2:a:0]....
Instead, use
ffmpeg -f concat -i "${video_list_textfile}" -c copy "${full_video_path}"
where ${video_list_textfile} is a text file of the form
file 'file1.mp4'
file 'file2.mp4'
file 'file3.mp4'
...