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• Making a video with opencv and ffmpeg. How to find the right color format ?

  19 décembre 2014, par luc

  I have a webcam video recorder program built with python, opencv and ffmpeg

  It works ok except that the color of the video is more blue than the reality. The problem seems to come from color format of images.

  It seems that OpenCv is giving BGR images and ffmpeg+libx264 is expecting YUV420p. I’ve read that YUV420p correspond to YCbCr.

  opencv has no conversion from BGR to YCbCr. It only has a conversion to YCrCb.

  I have made some searchs and tried different alternatives to try converting opencv image to something that could be ok for ffmpeg+libx264. None is working. At this point, I am a bit lost and I would appreciate any pointer that could help me to fix this color issue.

• ffmpeg - I want to concat multiple videos (front / rear) with overlay and one second delay

  12 mai 2024, par Andrej Florjančič

  I try to write bash script to concat front and rear video files with delay 1 second at start and overlay rear over front.

  


  I wrote the following bash script :

  


  # Define the output file
output_file="${VIDEO}/final_output_${choice}.mp4"

# Collect and sort the video files
front_files=( $(ls *_F.MP4 | sort) )
rear_files=( $(ls *_R.MP4 | sort) )

# Create a file to hold ffmpeg input commands and filter scripts
input_list="input_files.txt"
filter_script="filter_complex.txt"
inputs=""

# Clear the input list and filter script files
echo "" > "$input_list"
echo "" > "$filter_script"

# Number of files
num_files=${#front_files[@]}

# Iterate through the sorted files to build the filter script
for i in "${!front_files[@]}"; do
    echo "file '${front_files[$i]}'" >> "$input_list"
    echo "file '${rear_files[$i]}'" >> "$input_list"
    
    echo "[$((2*i)):v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_$i]; [$((2*i)):a]atrim=start=1,asetpts=PTS-STARTPTS[a_$i];" >> "$filter_script"
    echo "[$((2*i+1)):v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_$i];" >> "$filter_script"  # Rear video only
    echo "[f_$i][r_$i]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_$i];" >> "$filter_script"

    input+="[mix_$i][a_$i]"
done

# Concatenate all combined labels
echo "${input}concat=n=${#front_files[@]}:v=1:a=1[v][a]" >> "$filter_script"

# Run FFmpeg with filter script
ffmpeg -f concat -safe 0 -i "$input_list" \
    -filter_complex_script "$filter_script" \
    -map "[v]" -map "[a]" \
    -y "$output_file"


  


  This script generates two files input_list.txt :

  


  file '20200826_084407_F.MP4'
file '20200826_084407_R.MP4'
file '20200826_084708_F.MP4'
file '20200826_084708_R.MP4'
file '20200826_084910_F.MP4'
file '20200826_084910_R.MP4'


  


  filter_script.txt :

  


  [0:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_0]; [0:a]atrim=start=1,asetpts=PTS-STARTPTS[a_0];
[1:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_0];
[f_0][r_0]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_0];
[2:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_1]; [2:a]atrim=start=1,asetpts=PTS-STARTPTS[a_1];
[3:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_1];
[f_1][r_1]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_1];
[4:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_2]; [4:a]atrim=start=1,asetpts=PTS-STARTPTS[a_2];
[5:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_2];
[f_2][r_2]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_2];
[mix_0][a_0][mix_1][a_1][mix_2][a_2]concat=n=3:v=1:a=1[v][a]


  


  I'w got error :

  


  Input #0, concat, from 'input_files.txt':
  Duration: N/A, start: 0.000000, bitrate: 11973 kb/s
  Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 11877 kb/s, 30 fps, 30 tbr, 60k tbn, 60 tbc
    Metadata:
      creation_time   : 2020-08-26T08:47:07.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : h264
  Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 96 kb/s
    Metadata:
      creation_time   : 2020-08-26T08:47:07.000000Z
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Invalid file index 1 in filtergraph description
[0:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_0]; [0:a]atrim=start=1,asetpts=PTS-STARTPTS[a_0];
[1:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_0];
[f_0][r_0]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_0];
[2:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_1]; [2:a]atrim=start=1,asetpts=PTS-STARTPTS[a_1];
[3:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_1];
[f_1][r_1]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_1];
[4:v]trim=start=1,scale=1920:1080,setpts=PTS-STARTPTS[f_2]; [4:a]atrim=start=1,asetpts=PTS-STARTPTS[a_2];
[5:v]trim=start=1,scale=640:360,setpts=PTS-STARTPTS[r_2];
[f_2][r_2]overlay=x=(main_w-overlay_w-10):y=(main_h-overlay_h-10)[mix_2];
[mix_0][a_0][mix_1][a_1][mix_2][a_2]concat=n=3:v=1:a=1[v][a]


  


  What am I doing wrong ?

  


• ffmpeg hardwareaccleration using —enable-nvenc giving errors in vs 2012

  3 octobre 2020, par user2290878

  am trying to compile ffmpeg with nvenc enabled using msvc toolchain with vs 2012 , its giving error ,

  


  ERROR : nvenc requested but not found

  


  following error logs is seen in config.log :

  


  c99wrap cl -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -Dstrtod=avpriv_strtod -Dsnprintf=avpriv_snprintf -D_snprintf=avpriv_snprintf -Dvsnprintf=avpriv_vsnprintf -D_USE_MATH_DEFINES -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_WIN32_WINNT=0x0502 -nologo -Dstrtoll=_strtoi64 -Dstrtoull=_strtoui64 -Z7 -W4 -wd4244 -wd4127 -wd4018 -wd4389 -wd4146 -wd4057 -wd4204 -wd4706 -wd4305 -wd4152 -wd4324 -we4013 -wd4100 -wd4214 -wd4307 -wd4273 -wd4554 -wd4701 -O2 -Oy- -FIstdlib.h -c -Fo./ffconf.VPz0M2D2.o ./ffconf.hc8dkH6N.c
ffconf.hc8dkH6N.c
ffconf.VPz0M2D2.o_converted.c
./ffconf.hc8dkH6N.c(1) : warning C4431: missing type specifier - int assumed. Note: C no longer supports default-int
./ffconf.hc8dkH6N.c(1) : error C2054: expected '(' to follow 'inline'
./ffconf.hc8dkH6N.c(1) : error C2085: 'foo' : not in formal parameter list
./ffconf.hc8dkH6N.c(1) : error C2143: syntax error : missing ';' before '{'
check_host_cc
BEGIN ./ffconf.hc8dkH6N.c
    1   static inline int foo(int a) { return a; }
END ./ffconf.hc8dkH6N.c
c99wrap cl -nologo -W4 -wd4244 -wd4127 -wd4018 -wd4389 -wd4146 -wd4057 -wd4204 -wd4706 -wd4305 -wd4152 -wd4324 -we4013 -wd4100 -wd4214 -wd4307 -wd4273 -wd4554 -wd4701 -O3 -c -Fo./ffconf.VPz0M2D2.o ./ffconf.hc8dkH6N.c
cl : Command line warning D9002 : ignoring unknown option '-O3'
ffconf.hc8dkH6N.c
cl : Command line warning D9002 : ignoring unknown option '-O3'
ffconf.VPz0M2D2.o_converted.c
./ffconf.hc8dkH6N.c(1) : warning C4431: missing type specifier - int assumed. Note: C no longer supports default-int
./ffconf.hc8dkH6N.c(1) : error C2054: expected '(' to follow 'inline'
./ffconf.hc8dkH6N.c(1) : error C2085: 'foo' : not in formal parameter list
./ffconf.hc8dkH6N.c(1) : error C2143: syntax error : missing ';' before '{'
ERROR: nvenc requested but not found