Reputation: 1
FFmpeg disrupting "while/if" structure in Bash/shell scripting - how to fix?
I'm trying to extract a set number of frames from a series of .mp4 videos within several folders. I'm reading in variables from a CSV file, where each row of the CSV file contains the variables for each clip, which are: "dataset", "file name", "framelabel", "clip target start time", "clip target end time", "extract rate" (in seconds per frame), and "reason for exclusion."
I'm using a while/if loop structure so I can avoid trying to process the videos that are excluded from our project.
The while/if loop structure seems to work well when I just print out the variable names. However, when I insert a line of ffmpeg code, the variable assignments for the next video (ie, the following line read from the CSV file) go haywire.
Here is the code WITHOUT the ffmpeg line, which seems to work (all the "echo" statements are just there as debugging aids to track the variable assignments):
IFS=‘,’
while read DATASET FILENAME FRAMELABEL TARGET_START TARGET_END TOTAL_DURATION EXTRACT_RATE REASON_FOR_EXCLUSION
do
echo “PRE FFMPEG”
echo “dataset and filename are “ $DATASET/$FILENAME
echo “target start is “ $TARGET_START
echo “target end is “ $TARGET_END
if [ $TARGET_START != EXCLUDED ] && [ $TARGET_START != Target_start ]
then
IFS=‘:’
read -r -a fps_array <<< "$EXTRACT_RATE"
IFS=‘,’
let "secs = ${fps_array[0]}*3600 + ${fps_array[1]}*60 + ${fps_array[2]}"
FPS_RATE=$(echo "scale=20;1/$secs" | bc)
echo “AFTER FFMPEG”
echo “dataset and filename are “ $DATASET/$FILENAME
echo “target start is “ $TARGET_START
echo “target end is “ $TARGET_END
fi
done < Test_Key.csv`
The output for the code above looks like this, which is correct (I have 2 folders, "cats" and "es123", with two videos each; one of the es123 videos is excluded from frame extraction):
“PRE FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
“AFTER FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
“PRE FFMPEG”
“dataset and filename are “ cats/IMG_4137
“target start is “ 0:00:10
“target end is “ 0:00:40
“AFTER FFMPEG”
“dataset and filename are “ cats/IMG_4137
“target start is “ 0:00:10
“target end is “ 0:00:40
“PRE FFMPEG”
“dataset and filename are “ es123/IMG_4577
“target start is “ EXCLUDED
“target end is “
“PRE FFMPEG”
“dataset and filename are “ es123/IMG_4839
“target start is “ 0:00:05
“target end is “ 0:00:25
“AFTER FFMPEG”
“dataset and filename are “ es123/IMG_4839
“target start is “ 0:00:05
“target end is “ 0:00:25
However, I then try to add my ffmpeg line in that does the actual frame extraction:
IFS=‘,’
while read DATASET FILENAME FRAMELABEL TARGET_START TARGET_END TOTAL_DURATION EXTRACT_RATE REASON_FOR_EXCLUSION
do
echo “PRE FFMPEG”
echo “dataset and filename are “ $DATASET/$FILENAME
echo “target start is “ $TARGET_START
echo “target end is “ $TARGET_END
if [ $TARGET_START != EXCLUDED ] && [ $TARGET_START != Target_start ]
then
IFS=‘:’
read -r -a fps_array <<< "$EXTRACT_RATE"
IFS=‘,’
let "secs = ${fps_array[0]}*3600 + ${fps_array[1]}*60 + ${fps_array[2]}"
FPS_RATE=$(echo "scale=20;1/$secs" | bc)
ffmpeg -i $DATASET/$FILENAME.mp4 -ss $TARGET_START -to $TARGET_END -vf fps=$FPS_RATE ${DATASET}/${DATASET}_${FILENAME}_%03d.jpg
echo “AFTER FFMPEG”
echo “dataset and filename are “ $DATASET/$FILENAME
echo “target start is “ $TARGET_START
echo “target end is “ $TARGET_END
fi
done < Test_Key.csv
The result is that frames are correctly extracted for the first movie, but then the variable names for the second movie are completely screwed up (and then, of course, the code fails because the video names are wrong). You can see this in the 'echo' statements I used to track the variable naming, which become:
“PRE FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
“AFTER FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
“PRE FFMPEG”
“dataset and filename are “ IMG_4839/es123_2
“target start is “ 0:00:25
“target end is “ 0:00:20
Does anyone know why ffmpeg is affecting the functioning of the while/if loop structure here? (I'm pretty new to shell scripting, sorry if this is something obvious). And what I can do to fix it?
Thank you!
For reference, here is everything printed when I run the code with the ffmpeg line included-- there are some parse errors showing up that I don't really understand but probably explain this.
“PRE FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
ffmpeg version 4.2.2-tessus https://evermeet.cx/ffmpeg/ Copyright (c) 2000-2019 the FFmpeg developers
built with Apple clang version 11.0.0 (clang-1100.0.33.16)
configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libmysofa --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvmaf --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-version3 --pkg-config-flags=--static --disable-ffplay
libavutil 56. 31.100 / 56. 31.100
libavcodec 58. 54.100 / 58. 54.100
libavformat 58. 29.100 / 58. 29.100
libavdevice 58. 8.100 / 58. 8.100
libavfilter 7. 57.100 / 7. 57.100
libswscale 5. 5.100 / 5. 5.100
libswresample 3. 5.100 / 3. 5.100
libpostproc 55. 5.100 / 55. 5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'cats/IMG_3460.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.29.100
Duration: 00:00:25.15, start: 0.000000, bitrate: 6866 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x1920, 6796 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
Metadata:
handler_name : Core Media Video
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 69 kb/s (default)
Metadata:
handler_name : Core Media Audio
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
Press [q] to stop, [?] for help
Enter command: <target>|all <time>|-1 <command>[ <argument>]
Parse error, at least 3 arguments were expected, only 1 given in string 'ats,IMG_4137,cats_2,0:00:10,0:00:40,0:00:30,0:00:03,none,,'
[swscaler @ 0x7fd3fc953400] deprecated pixel format used, make sure you did set range correctly
Output #0, image2, to 'cats/cats_IMG_3460_%03d.jpg':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.29.100
Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 1080x1920, q=2-31, 200 kb/s, 0.50 fps, 0.50 tbn, 0.50 tbc (default)
Metadata:
handler_name : Core Media Video
encoder : Lavc58.54.100 mjpeg
Side data:
cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
frame= 8 fps=3.2 q=1.6 size=N/A time=00:00:16.00 bitrate=N/A speed=6.33x 0.00 bitrate=N/A speed=6.59x
Enter command: <target>|all <time>|-1 <command>[ <argument>]
Parse error, at least 3 arguments were expected, only 1 given in string 'LUDED,,,,boring,,'
frame= 11 fps=3.0 q=2.6 L00120000000000000000000000000000size=N/A time=00:00:22.00 bitrate=N/A speed=6.06x
video:803kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
“AFTER FFMPEG”
“dataset and filename are “ cats/IMG_3460
“target start is “ 0:00:02
“target end is “ 0:00:24
“PRE FFMPEG”
“dataset and filename are “ IMG_4839/es123_2
“target start is “ 0:00:25
“target end is “ 0:00:20
-bash: let: secs = none*3600 + *60 + : syntax error: operand expected (error token is "*60 + ")
ffmpeg version 4.2.2-tessus https://evermeet.cx/ffmpeg/ Copyright (c) 2000-2019 the FFmpeg developers
built with Apple clang version 11.0.0 (clang-1100.0.33.16)
configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libmysofa --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvmaf --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-version3 --pkg-config-flags=--static --disable-ffplay
libavutil 56. 31.100 / 56. 31.100
libavcodec 58. 54.100 / 58. 54.100
libavformat 58. 29.100 / 58. 29.100
libavdevice 58. 8.100 / 58. 8.100
libavfilter 7. 57.100 / 7. 57.100
libswscale 5. 5.100 / 5. 5.100
libswresample 3. 5.100 / 3. 5.100
libpostproc 55. 5.100 / 55. 5.100
IMG_4839/es123_2.mp4: No such file or directory
“AFTER FFMPEG”
“dataset and filename are “ IMG_4839/es123_2
“target start is “ 0:00:25
“target end is “ 0:00:20
Upvotes: 0
Views: 269
Answers (1)
Reputation: 482
From FFmpeg's manual:
-stdin Enable interaction on standard input. On by default unless standard input is used as an input. To explicitly disable interaction you need to specify "-nostdin".
In your case, passing -nostdin to the FFmpeg CLI proc should be enough.
If you had several loops, you could also use different FDs, for example:
while read DATASET FILENAME FRAMELABEL TARGET_START TARGET_END TOTAL_DURATION EXTRACT_RATE REASON_FOR_EXCLUSION <&3 ;do
...
done 3< Test_Key.csv
The key change here is of course the 3.
Upvotes: 3
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