Merge pull request #11 from valnoel/develop

HotFix: make OutputFile::getProgressDuration() virtual
Transcoder: call init in process method

* No need to expect the user to call init() before process().
* Note: the init() method can be called several times with no side
effects.
* Update pyTest.
Transcoder: add private method getTotalDurationFromProcessMethod

In order to simplify process method.
Transcoder: refactore process

* Clean indentation.
* Avoid while( 1 ).
* Suppress warning of getTotalDurationFromProcessMethod: add default case in switch.
Transcoder: add private method manageInfinityStreamFromProcessMethod

Can call setProcessMethod before adding the streams.
genericProcessor: clean

* Remove comment.
* No need to call init().
Transcoder: manage FFmpeg log level

* Set it to AV_LOG_QUIET in Transcoder constructor.
* Set it to AV_LOG_DEBUG if setVerbose of Transcoder to true.
InputFile: into readNextPacket, return expected data (instead of caching it)
AvInputStream: extract data from file only if the stream cache is empty
Clean use of av_strerror

* Use macro AV_ERROR_MAX_STRING_SIZE.
* Get size of errbuf with sizeof array.
Merge pull request #14 from valnoel/fix_read_next_packet

Avoid a copy of packet data when readNextPacket
Merge pull request #13 from cchampet/fix_message_error_buffer_size

Clean use of av_strerror
Merge pull request #12 from cchampet/move_init_to_process

Transcoder clean