player: fix --lavfi-complex freeze

Commit 0e0b87b6f3297 fixed that dropped packets did not trigger further
work correctly. But it also made trivial --lavfi-complex freeze. The
reason is that the meaning if DATA_AGAIN was overloaded: the decoders
meant that they should be called again, while lavfi.c meant that other
outputs needed to be checked again. Rename the latter meaning to
DATA_STARVE, which means that the current input will deliver no more
data, until "other" work has been done (like reading other outputs, or
feeding input).

The decoders never return DATA_STARVE, because they don't get input from
the player core (instead, they get it from the demuxer directly, which
is why they still can return DATA_WAIT).

Also document the DATA_* semantics in the enum.

Fixes #4746.

1 files changed, 4 insertions, 4 deletions

diff --git a/player/lavfi.c b/player/lavfi.c
index 5183b0e690..c597387937 100644
--- a/player/lavfi.c
+++ b/player/lavfi.c
@@ -716,12 +716,12 @@ static int lavfi_request_frame(struct lavfi_pad *pad)
     } else if (pad->main->all_waiting) {
         return DATA_WAIT;
     }
-    return DATA_AGAIN;
+    return DATA_STARVE;
 }
 
 // Try to read a new frame from an output pad. Returns one of the following:
 //      DATA_OK: a frame is returned
-//      DATA_AGAIN: needs more input data
+//      DATA_STARVE: needs more input data
 //      DATA_WAIT: needs more input data, and all inputs in LAVFI_WAIT state
 //      DATA_EOF: no more data
 int lavfi_request_frame_a(struct lavfi_pad *pad, struct mp_audio **out_aframe)
@@ -750,7 +750,7 @@ bool lavfi_needs_input(struct lavfi_pad *pad)
 
 // A filter user is supposed to call lavfi_needs_input(), and if that returns
 // true, send either a new status or a frame. A status can be one of:
-//      DATA_AGAIN: a new frame/status will come, caller will retry
+//      DATA_STARVE: a new frame/status will come, caller will retry
 //      DATA_WAIT: a new frame/status will come, but caller goes to sleep
 //      DATA_EOF: no more input possible (in near time)
 // If you have a new frame, use lavfi_send_frame_ instead.
@@ -764,7 +764,7 @@ void lavfi_send_status(struct lavfi_pad *pad, int status)
     assert(!pad->pending_v && !pad->pending_a);
 
     pad->input_waiting = status == DATA_WAIT || status == DATA_EOF;
-    pad->input_again = status == DATA_AGAIN;
+    pad->input_again = status == DATA_STARVE;
     pad->input_eof = status == DATA_EOF;
 }