Tag Archives: convert

Convert FLV to MP4

Quick and dirty lines to convert FLV files into MP4.

To do so, you need the package ffmpeg.

# Temporary move all the .flv files into a TMP directory
$ find . -type f -name "*.flv" -exec mv {} ../TMP/ \;

# Remove all spaces from the filename
$ cd ../TMP/
$ for file in *' '* ; do mv -- "$file" "${file// /_}" ; done

# Now, convert all the files from FLV to MP4 using ffmpeg
$ for file in `ls` ; do ffmpeg -i "$file" -c copy "${file//flv/mp4}" ; done

During the process, you might get some errors. You will see some .mp4 files with size 0 bites.

You can then try to remove the broken files and try converting re-encoding

# Find and delete files size 0
$ find . -type f -size 0 -print0 | xargs -0 rm

# Try re-encoding
$ for file in `ls *.flv` ; do ffmpeg -i "$file" -vcodec libx264 -acodec copy "${file//flv/mp4}" ; done

Manage PDF files

Merge multiple files into single PDF

I’m sure that we all had the need to send a single PDF file, maybe a signed contract. Yes, those 20 or more pages that you need to return, probably with just two of them filled up and signed.

Some PDF give you the ability to digitally sign them. But in my experience, most of them aren’t so modern.

So, what do I do?

I print ONLY the pages that I need to sign, scan them and here I am, with the need to “rebuild” the PDF, replacing the pages signed.

Example.
You have the file contract.pdf, with 20 pages and you need to sign page 10 and page 20.
The scan has a different resolution (or, even worse, it’s a different format, like jpg).

Here the command to make the magic happen:

convert contract.pdf[0-8] mypage10.jpg contract.pdf[10-18] mypage20.jpg -resize 1240x1753 -extent 1240x1753 -gravity center -units PixelsPerInch -density 150x150 contract_signed.pdf

The bit before -resize is pretty self explanatory. The bit after is a way to have the size of all pages fitting an A4 format, with a good printable resolution.

Of course, to make this happen, you need Linux (or WSL on Windows 10) and imagemagick installed.

Another way is using ghostscript.

A simple Ghostscript command to merge two PDFs in a single file is shown below:

gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=combine.pdf -dBATCH 1.pdf 2.pdf

What about a quick onliner to reduce and convert to grayscale your pdf?

ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -sProcessColorModel=DeviceGray -sColorConversionStrategy=Gray -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

PDF size reduce

Sometimes instead, you need to reduce the size of an existing PDF. Here a handy oneliner, using ghostscript:

ghostscript -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/printer -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Other options for PDFSETTINGS:

  • /screen selects low-resolution output similar to the Acrobat Distiller “Screen Optimized” setting.
  • /ebook selects medium-resolution output similar to the Acrobat Distiller “eBook” setting.
  • /printer selects output similar to the Acrobat Distiller “Print Optimized” setting.
  • /prepress selects output similar to Acrobat Distiller “Prepress Optimized” setting.
  • /default selects output intended to be useful across a wide variety of uses, possibly at the expense of a larger output file.

Happy PDF’ing 🙂

Sources:
https://stackoverflow.com/questions/23214617/imagemagick-convert-image-to-pdf-with-a4-page-size-and-image-fit-to-page
https://www.shellhacks.com/merge-pdf-files-linux-command-line/
https://gist.github.com/firstdoit/6390547

MySQL Engine – InnoDB vs MyISAM

InnoDB does locking on the row level and runs queries as nonlocking consistent reads by default

How to check the engine of tables for a database

mysql> select engine from tables.information_schema where table_schema='<DB_NAME>';

 

Summary of Engines’ space utilised

select engine,sum(index_length+data_length)/1024/1024,count(engine) from information_schema.tables group by engine;

 

Check MyISAM tables

NOTE:

When it converts from MyISAM to InnoDB, you will see in process list ‘copy to tmp table’. This has nothing to do with tmp_table_size or tmpdir. What it does, it goes inside your /var/lib/mysql/<dbname>/ and creates temporary files called like #sqlXXXX.frm and #sqlXXXX.ibd. Keep an eye on the size of the .ibd file to monitoring the progression. It should be roughly big like the sum of <table>.MYI and <table>.MYD. +~20%

 

SELECT table_schema,table_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA NOT IN ("information_schema", "performance_schema", "mysql") and engine = 'MyISAM';

Change all to InnoDB
https://support.rackspace.com/how-to/mysql-engines-myisam-vs-innodb/
When?
https://docs.dev4press.com/tutorial/wordpress/choosing-mysql-database-engine-myisam-or-innodb/
Quick answer: Always EXCEPT If you want to use FULLTEXT or SPATIAL indexes for some tables: in this case there is no choice and you must use MyISAM.

NOTE: FULLTEXT index support for InnoDB tables requires MySQL 5.6.4 or higherMariaDB 10.0.5 or higher
Highly recommend upgrading to MariaDB 10.0 as this is the 5.6 MySQL equivalent. It does not alter the data structures as 5.6 does and can be downgraded much more easily. It contains all the features of 5.6 plus more as well as being a drop-in replacement for MySQL in RHEL7.
I would point you to these KB articles:
https://mariadb.com/kb/en/mariadb-vs-mysql-features/https://mariadb.com/kb/en/mariadb/mariadb-vs-mysql-compatibility/Repositories: https://downloads.mariadb.org/mariadb/repositories/#mirror=somerset

Check if there are FULLTEXT or SPATIAL indexes:

mysql> use information_schema;
mysql> SELECT DISTINCT CONCAT(STATISTICS.TABLE_SCHEMA, '.', STATISTICS.TABLE_NAME) AS fulltext_table, (TABLES.DATA_LENGTH + TABLES.INDEX_LENGTH)/1024/1024 AS size_M FROM STATISTICS INNER JOIN TABLES ON TABLES.TABLE_SCHEMA = STATISTICS.TABLE_SCHEMA AND TABLES.TABLE_NAME = STATISTICS.TABLE_NAME WHERE STATISTICS.INDEX_TYPE IN ("SPATIAL", "FULLTEXT") GROUP BY STATISTICS.TABLE_SCHEMA, STATISTICS.TABLE_NAME;

Convert ALL MyISAM tables to InnoDB (all databases):

2 steps + backup

# mysql --batch --skip-column-names --execute 'select concat("alter table ",TABLE_SCHEMA,".",TABLE_NAME," ENGINE='MyISAM';") from information_schema.TABLES where ENGINE = "MyISAM" AND TABLE_SCHEMA NOT IN ("information_schema", "performance_schema", "mysql");' > rollback_all2Innodb.sql
# mysql --batch --skip-column-names --execute 'select concat("alter table ",TABLE_SCHEMA,".",TABLE_NAME," ENGINE='InnoDB';") from information_schema.TABLES where ENGINE = "MyISAM" AND TABLE_SCHEMA NOT IN ("information_schema", "performance_schema", "mysql");' > all2Innodb.sql
# mysql < all2Innodb.sql

(one liner – CAREFUL!)

# mysql --batch --skip-column-names --execute 'select concat("alter table ",TABLE_SCHEMA,".",TABLE_NAME," ENGINE='InnoDB';") from information_schema.TABLES where ENGINE = "MyISAM" AND TABLE_SCHEMA NOT IN ("information_schema", "performance_schema", "mysql");' | mysql

 

Convert MyISAM tables of a SPECIFIC database to InnoDB:

Backup and convert-file

# DB="<dbname>"
# mysql --batch --skip-column-names --execute "select concat('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' ENGINE = \'MyISAM\';') from information_schema.TABLES where TABLE_SCHEMA = '"$DB"' and ENGINE = 'MyISAM';" > rollback_$DB_all2Innodb.sql

# mysql --batch --skip-column-names --execute "select concat('alter table ',TABLE_SCHEMA,'.',TABLE_NAME,' ENGINE = \'InnoDB\';') from information_schema.TABLES where TABLE_SCHEMA = '"$DB"' and ENGINE = 'MyISAM';" > $DB_all2Innodb.sql

NOTE: When it converts from MyISAM to InnoDB, you will see in process list ‘copy to tmp table’. This has nothing to do with tmp_table_size or tmpdir. What it does, it goes inside your /var/lib/mysql/<dbname>/ and creates temporary files called like #sqlXXXX.frm and #sqlXXXX.ibd. Keep an eye on the size of the .ibd file to monitoring the progression. It should be roughly big like the sum of <table>.MYI and <table>.MYD. +~20%