DTS was used in ChunkingHandler. As a result, SegmentInfo contained
timestamp in DTS. MP4Muxer has a logic to change SegmentInfo to use
PTS but not in other muxers.
Benefits of using PTS in ChunkingHandler:
- De-dup the redundant logic in MP4Muxer
- Ensure consistent behavior in different output containers
- Consistent with other timestamps, e.g. Ad Cue timestamps
Issue #413
Change-Id: Ib671badf144e0c0866d60f4ff0ac0cbbdd33817e
This handler is a multi-in multi-out handler. If more than one input is
provided, there should be one and only one video stream; also, all inputs
should come from the same thread and are synchronized.
There can be multiple chunking handler running in different threads or even
different processes, we use the "consistent chunking algorithm" to make sure
the chunks in different streams are aligned without explicit communcating
with each other - which is not efficient and often difficult.
Consistent Chunking Algorithm:
1. Find the consistent chunkable boundary
Let the timestamps for video frames be (t1, t2, t3, ...). Then a
consistent chunkable boundary is simply the first chunkable boundary after
(tk / N) != (tk-1 / N), where '/' denotes integer division, and N is the
intended chunk duration.
2. Chunk only at the consistent chunkable boundary
This algorithm will make sure the chunks from different video streams are
aligned if they have aligned GoPs. However, this algorithm will only work
for video streams. To be able to chunk non video streams at similar
positions as video streams, ChunkingHandler is designed to accept one video
input and multiple non video inputs, the non video inputs are chunked when
the video input is chunked. If the inputs are synchronized - which is true
if the inputs come from the same demuxer, the video and non video chunks
are aligned.
Change-Id: Id3bad51ab14f311efdb8713b6cd36d36cf9e4639
KongQun Yang
Aaron Vaage
Kamesh Devarakonda