// -1 means we want to send from the end of the backlog (the normal case),
// although only at a keyframe.
// -2 means we want to send from the _beginning_ of the backlog.
// -1 means we want to send from the end of the backlog (the normal case),
// although only at a keyframe.
// -2 means we want to send from the _beginning_ of the backlog.
// Once we go into WAITING_FOR_KEYFRAME, PREBUFFERING or SENDING_DATA,
// these negative values will be translated to real numbers.
size_t stream_pos = 0;
// Position at which to end the stream (one-past-the-end, used for fragments).
// -1 means never to end; this is the common case.
// Once we go into WAITING_FOR_KEYFRAME, PREBUFFERING or SENDING_DATA,
// these negative values will be translated to real numbers.
size_t stream_pos = 0;
// Position at which to end the stream (one-past-the-end, used for fragments).
// -1 means never to end; this is the common case.