MPEG4Writer: Write a zero-length compressor string

The first byte is the number of bytes in the string to display,
the rest is the actual string (see ISO/IEC 14496-12:2008 page 29,
compressorname in VisualSampleEntry) to display. Currently, all 31
space characters are displayed in certain players (such as Apple
QuickTime Player) instead of the plain codec name (e.g. "H.264").
By writing the string length properly, the actual content of the
remaining 31 bytes is ignored instead of displayed.

Change-Id: I7f93a8966d74a4e86abc46c3dcb70f71780d9cd6
SoftVorbis: Set the right encoding in the port definition

Previously, it set the encoding type to AAC, which is just a typo.

Change-Id: I2dcae1f579e9feb0b35b6f5d334028c534275042
SoftAMR: Signal the right frame format

The correct enum for the format used is OMX_AUDIO_AMRFrameFormatFSF,
which is the same as is used in amrnb/enc/SoftAMRNBEncoder.cpp,
amrwbenc/SoftAMRWBEncoder.cpp and in OMXCodec and ACodec.

The OMX_AUDIO_AMRFrameFormatConformance enum refers to an odd file
format only used for conformance tests, not used in the wild.

Change-Id: Idc395fc1d4969e33453522d6ec6526876438c526
Avoid invalid memory access when using extractMetadata()

BpMediaMetadataRetriever::extractMetadata() returns a string
which is returned by readCString() function of the reply parcel object.
However, the parcel object is destroyed at the end of the
extractMetadata() function, and so the returned pointer is invalid.
This patch fixes this problem by storing the metadata string value.

Change-Id: I2a2ccba78246175b2845a237679d6cebe881e83b
Signed-off-by: Sangkyu Lee <sk82.lee@lge.com>