Certain functions such as avformat_open_input and av_read_frame can
block, causing the program to someone wait very long periods of time
when a network URL is used with the media source. The
interrupt_callback member variable in AVFormatContext allows safely
canceling IO operations when trying to shut down or stop the
media-playback interface.
(Note: This commit also modifies deps/media-playback)
Allows buffering network-based media sources where supported. Default
is two megabytes of buffering.
Currently, when media-playback is used with a network address, video has
to wait for the first keyframe before it starts decoding. This is
probably not wise because the first packet of video may contain
additional header information, and because audio is forced to wait and
buffer while waiting for a keyframe, potentially causing a lot of audio
to get backed up unnecessarily which could inadvertently cause sync or
audio playback issues.
So, instead of waiting for a keyframe before decoding starts, decode
right away, and make it wait for a keyframe before calling the video
callback instead.
When media returns frames with negative linesizes, it means they're
inverted RGB formats and start from the last line of the image and move
back to the top via the negative linesize number. This would cause a
crash because this wasn't being taken in to account, and it would
traverse in to invalid memory.
Fixes potential decoding errors with FFmpeg's new decode API. Because
avcodec_send_packet may process multiple packets, you must call
avcodec_receive_frame continually until no more frames are left.
Failure to decode is unfortunately quite common with certain file types,
and is most of the time safely recoverable. There's no reason to
actually output a log message for this unless really needed.
Intended to replace libff as the media playback library. Intended to
use less threads and be more extensible. It was nearly impossible to
modify libff without bursting a vein.
