* Use Frame class instead (allocation/free is managed by the class).

Use VideoProperties::getProfile() method.

Use Frame::getEncodedSize() method.

* Use VideoProperties::getGopSize() instead.
* Add doc to this method.

* To get the level of analysis asked inside member methods.
* Will be used in the next commit.

* AVCodecContext->gop_size is unused when decode according to the ffmpeg
documentation:
https://ffmpeg.org/doxygen/2.8/structAVCodecContext.html#a9b6b3f1fcbdcc2ad9f4dbb4370496e38
* So compute this info when analyseGopStructure, and store it inside the
VideoProperties class.
* Because the gop size could be used inside getBitRate() method, throw a
runtime exception before using it.

* Before: picture type, is key frame
* After: picture type, encoded frame size in bytes
* Note: "is key frame" info can be found using the picture type (I
frame).

…perties

Throw a runtime_error if the duration is unknown.

…rties

* These instructions make analysis impossible for some AVC Intra media.
* WARNING: need to check if this commit induces some side effects.

The C++ structure was updated in commit:
81bc92e

This check is already done by av_get_profile_name method.

To improve readability.

All properties have the same value if not found.

…t gop

All properties have the same value if not found.

Revert of commit 5625a87

Like other getter to properties.

Avoid RuntimeError: basic_string::_S_construct null not valid.

Need to analyse first GOP to compute bitrate and get gop size of output.