According to the PIFF specification[1] the base_data_offset field MUST be
omitteed. See section 5.2.17. Since the ISMV files created by ffmpeg state
that they are 'piff' compatible via 'ftyp' box, this needs to be corrected.

[1] http://www.iis.net/learn/media/smooth-streaming/protected-interoperable-file-formatSigned-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This commit is based on libav's implementation and
makes sure to compare output timestamps together.
It also reduces the differences with avconv.

The changes to the test reference files are caused
by an additional packet at the end, the timestamp
of the frame encoded by this packet is always
strictly below the limit stated by the -t option.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>