[FFmpeg-user] how to use ocr in ffmpeg to produce text message

[Paul B Mahol]

On 6/29/18, qw <applemax82 at 163.com> wrote:
> Hi,
>
>
> ocr is new in ffmpeg 4.0.
>
>
> 1)
> I build ffmpeg 4.0 and its tesseract-3.05.01, and copy english training data
> to /usr/local/share/tessdata/eng.traineddata.
>
>
> I use the following command to run ocr filter in ffmpeg, but fail to find
> eng.traineddata. But I have set TESSDATA_PREFIX:
> TESSDATA_PREFIX=/usr/local/share LD_LIBRARY_PATH=/usr/local/lib
> /usr/local/bin/ffmpeg -f lavfi -i "movie=test_ocr.png,
> ocr=datapath=tessdata:language=eng, drawgraph=lavfi.ocr.text"
> test_ocr_out.png
>
>
> ffmpeg version 4.0 Copyright (c) 2000-2018 the FFmpeg developers
>   built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-16)
>   configuration: --enable-version3 --enable-asm --enable-x86asm
> --enable-avfilter --disable-static --enable-shared --enable-gpl
> --enable-nonfree --prefix=/usr/local/ --enable-libvidstab --enable-libass
> --enable-libfreetype --extra-libs=-lfreetype --enable-libtesseract
> --enable-libfdk_aac --enable-libmp3lame --enable-libx264
> --enable-libopenjpeg --enable-libwebp --enable-libx265 --enable-libvorbis
> --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib
> --enable-stripping --enable-libmfx
>   libavutil      56. 14.100 / 56. 14.100
>   libavcodec     58. 18.100 / 58. 18.100
>   libavformat    58. 12.100 / 58. 12.100
>   libavdevice    58.  3.100 / 58.  3.100
>   libavfilter     7. 16.100 /  7. 16.100
>   libswscale      5.  1.100 /  5.  1.100
>   libswresample   3.  1.100 /  3.  1.100
>   libpostproc    55.  1.100 / 55.  1.100
> Error opening data file /tessdata/eng.traineddata
> Please make sure the TESSDATA_PREFIX environment variable is set to the
> parent directory of your "tessdata" directory.
> Failed loading language 'eng'
> Tesseract couldn't load any languages!
> [Parsed_ocr_1 @ 0x1e03d80] failed to init tesseract
> [lavfi @ 0x1df77c0] Error initializing filter 'ocr' with args
> 'datapath=tessdata:language=eng'
> movie=test_ocr.png, ocr=datapath=tessdata:language=eng,
> drawgraph=lavfi.ocr.text: Invalid argument
>
>
>
>
> If I set TESSDATA_PREFIX to /usr/local/share/tessdata, the same error
> occurs:
>
>
> TESSDATA_PREFIX=/usr/local/share/tessdata LD_LIBRARY_PATH=/usr/local/lib
> /usr/local/bin/ffmpeg -f lavfi -i "movie=test_ocr.png,
> ocr=datapath=tessdata:language=eng, drawgraph=lavfi.ocr.text"
> test_ocr_out.png
>
>
> ffmpeg version 4.0 Copyright (c) 2000-2018 the FFmpeg developers
>   built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-16)
>   configuration: --enable-version3 --enable-asm --enable-x86asm
> --enable-avfilter --disable-static --enable-shared --enable-gpl
> --enable-nonfree --prefix=/usr/local/ --enable-libvidstab --enable-libass
> --enable-libfreetype --extra-libs=-lfreetype --enable-libtesseract
> --enable-libfdk_aac --enable-libmp3lame --enable-libx264
> --enable-libopenjpeg --enable-libwebp --enable-libx265 --enable-libvorbis
> --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib
> --enable-stripping --enable-libmfx
>   libavutil      56. 14.100 / 56. 14.100
>   libavcodec     58. 18.100 / 58. 18.100
>   libavformat    58. 12.100 / 58. 12.100
>   libavdevice    58.  3.100 / 58.  3.100
>   libavfilter     7. 16.100 /  7. 16.100
>   libswscale      5.  1.100 /  5.  1.100
>   libswresample   3.  1.100 /  3.  1.100
>   libpostproc    55.  1.100 / 55.  1.100
> Error opening data file /tessdata/eng.traineddata
> Please make sure the TESSDATA_PREFIX environment variable is set to the
> parent directory of your "tessdata" directory.
> Failed loading language 'eng'
> Tesseract couldn't load any languages!
> [Parsed_ocr_1 @ 0x18a8d80] failed to init tesseract
> [lavfi @ 0x189c7c0] Error initializing filter 'ocr' with args
> 'datapath=tessdata:language=eng'
> movie=test_ocr.png, ocr=datapath=tessdata:language=eng,
> drawgraph=lavfi.ocr.text: Invalid argument
>
>
> If I use /usr/local/bin/tesseract to do the ocr task, there is no problem.
>
>
> Why ffmpeg and tesseract-3.05.01 can't find eng.traineddata?
>
>
>
>
> 2)
> How can I use ocr to parse text from png file, and output the text into some
> specified txt file?
>

Definetely by not using drawgraph, drawgraph parses numbers not text,
but I see you have much bigger issues.

>
>
>
> Thanks
>
>
> Regards
>
>
> Andrew
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