Configurable with --transport_stream_offset_ms.
This is needed to compensate for possible negative timestamps in
inputs, which could happen on ISO-BMFF with EditLists.
Issue #112.
Change-Id: I0fce8766c9df2911b9bb859c1e54052a8ed2abfb
Two-character ISO-639 code in --default_language was ignored due to
a bug in language code matching as the language code in stream is
always converted to 3-character code.
Fixes#371.
Change-Id: I8618938af583a417446636ff9efe1c72ce822c33