From 2b125425a66f54922e8aaf34c2a616c43f024f11 Mon Sep 17 00:00:00 2001
From: tobigun <tobigun@b956fd51-792f-4845-bead-9b4dfca2ff2c>
Date: Mon, 3 Nov 2008 01:15:43 +0000
Subject: improved seeking: - the position will not be set to non-keyframes
(AVSEEK_FLAG_ANY) anymore as it might result in gray or green pictures
(FFmpeg does not use the information of the last keyframe after seeking) -
after seeking the texture was not updated correctly. - some comments added
git-svn-id: svn://svn.code.sf.net/p/ultrastardx/svn/trunk@1497 b956fd51-792f-4845-bead-9b4dfca2ff2c
---
src/media/UVideo.pas | 135 ++++++++++++++++++++++++++++++++-------------------
1 file changed, 85 insertions(+), 50 deletions(-)
diff --git a/src/media/UVideo.pas b/src/media/UVideo.pas
index 06577d9e..197fc572 100644
--- a/src/media/UVideo.pas
+++ b/src/media/UVideo.pas
@@ -126,6 +126,7 @@ type
fFrameBuffer: PByte; //**< stores a FFmpeg video frame
fFrameTex: GLuint; //**< OpenGL texture for FrameBuffer
+ fFrameTexValid: boolean; //**< if true, fFrameTex contains the current frame
fTexWidth, fTexHeight: cardinal;
{$IFDEF UseSWScale}
@@ -137,11 +138,11 @@ type
fTimeBase: extended; //**< FFmpeg time base per time unit
fTime: extended; //**< video time position (absolute)
- fLoopTime: extended; //**< video time position (relative to current loop)
+ fLoopTime: extended; //**< start time of the current loop
procedure Reset();
- function DecodeFrame(var AVPacket: TAVPacket; out pts: double): boolean;
- procedure SynchronizeVideo(Frame: PAVFrame; var pts: double);
+ function DecodeFrame(): boolean;
+ procedure SynchronizeTime(Frame: PAVFrame; var pts: double);
procedure GetVideoRect(var ScreenRect, TexRect: TRectCoords);
@@ -240,6 +241,7 @@ begin
fTime := 0;
fStream := nil;
fStreamIndex := -1;
+ fFrameTexValid := false;
fEOF := false;
@@ -453,7 +455,7 @@ begin
fOpened := False;
end;
-procedure TVideoPlayback_FFmpeg.SynchronizeVideo(Frame: PAVFrame; var pts: double);
+procedure TVideoPlayback_FFmpeg.SynchronizeTime(Frame: PAVFrame; var pts: double);
var
FrameDelay: double;
begin
@@ -473,12 +475,21 @@ begin
fTime := fTime + FrameDelay;
end;
-function TVideoPlayback_FFmpeg.DecodeFrame(var AVPacket: TAVPacket; out pts: double): boolean;
+{**
+ * Decode a new frame from the video stream.
+ * The decoded frame is stored in fAVFrame. fTime is updated to the new frame's
+ * time.
+ * @param pts will be updated to the presentation time of the decoded frame.
+ * returns true if a frame could be decoded. False if an error or EOF occured.
+ *}
+function TVideoPlayback_FFmpeg.DecodeFrame(): boolean;
var
FrameFinished: Integer;
VideoPktPts: int64;
pbIOCtx: PByteIOContext;
errnum: integer;
+ AVPacket: TAVPacket;
+ pts: double;
begin
Result := false;
FrameFinished := 0;
@@ -555,9 +566,9 @@ begin
end;
pts := pts * av_q2d(fStream^.time_base);
- // synchronize on each complete frame
+ // synchronize time on each complete frame
if (frameFinished <> 0) then
- SynchronizeVideo(fAVFrame, pts);
+ SynchronizeTime(fAVFrame, pts);
end;
// free the packet from av_read_frame
@@ -569,13 +580,12 @@ end;
procedure TVideoPlayback_FFmpeg.GetFrame(Time: Extended);
var
- AVPacket: TAVPacket;
errnum: Integer;
- myTime: Extended;
+ NewTime: Extended;
TimeDifference: Extended;
DropFrameCount: Integer;
- pts: double;
i: Integer;
+ Success: boolean;
const
FRAME_DROPCOUNT = 3;
begin
@@ -585,41 +595,50 @@ begin
if fPaused then
Exit;
- // current time, relative to last fLoop (if any)
- myTime := Time - fLoopTime;
- // time since the last frame was returned
- TimeDifference := myTime - fTime;
-
- {$IFDEF DebugDisplay}
- DebugWriteln('Time: '+inttostr(floor(Time*1000)) + sLineBreak +
- 'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
- 'TimeBase: '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
- 'TimeDiff: '+inttostr(floor(TimeDifference*1000)));
- {$endif}
+ // requested stream position (relative to the last loop's start)
+ NewTime := Time - fLoopTime;
- // check if a new frame is needed
- if (fTime <> 0) and (TimeDifference < fTimeBase) then
+ // check if current texture still contains the active frame
+ if (fFrameTexValid) then
begin
- {$ifdef DebugFrames}
- // frame delay debug display
- GoldenRec.Spawn(200,15,1,16,0,-1,ColoredStar,$00ff00);
- {$endif}
+ // time since the last frame was returned
+ TimeDifference := NewTime - fTime;
{$IFDEF DebugDisplay}
- DebugWriteln('not getting new frame' + sLineBreak +
- 'Time: '+inttostr(floor(Time*1000)) + sLineBreak +
- 'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
- 'TimeBase: '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
- 'TimeDiff: '+inttostr(floor(TimeDifference*1000)));
+ DebugWriteln('Time: '+inttostr(floor(Time*1000)) + sLineBreak +
+ 'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
+ 'TimeBase: '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
+ 'TimeDiff: '+inttostr(floor(TimeDifference*1000)));
{$endif}
- // we do not need a new frame now
- Exit;
+ // check if last time is more than one frame in the past
+ if (TimeDifference < fTimeBase) then
+ begin
+ {$ifdef DebugFrames}
+ // frame delay debug display
+ GoldenRec.Spawn(200,15,1,16,0,-1,ColoredStar,$00ff00);
+ {$endif}
+
+ {$IFDEF DebugDisplay}
+ DebugWriteln('not getting new frame' + sLineBreak +
+ 'Time: '+inttostr(floor(Time*1000)) + sLineBreak +
+ 'VideoTime: '+inttostr(floor(fTime*1000)) + sLineBreak +
+ 'TimeBase: '+inttostr(floor(fTimeBase*1000)) + sLineBreak +
+ 'TimeDiff: '+inttostr(floor(TimeDifference*1000)));
+ {$endif}
+
+ // we do not need a new frame now
+ Exit;
+ end;
end;
- // update video-time to the next frame
- fTime := fTime + fTimeBase;
- TimeDifference := myTime - fTime;
+ {$IFDEF VideoBenchmark}
+ Log.BenchmarkStart(15);
+ {$ENDIF}
+
+ // fetch new frame (updates fTime)
+ Success := DecodeFrame();
+ TimeDifference := NewTime - fTime;
// check if we have to skip frames
if (TimeDifference >= FRAME_DROPCOUNT*fTimeBase) then
@@ -640,19 +659,18 @@ begin
// skip half of the frames, this is much smoother than to skip all at once
for i := 1 to DropFrameCount (*div 2*) do
- DecodeFrame(AVPacket, pts);
+ Success := DecodeFrame();
end;
- {$IFDEF VideoBenchmark}
- Log.BenchmarkStart(15);
- {$ENDIF}
-
- if (not DecodeFrame(AVPacket, pts)) then
+ // check if we got an EOF or error
+ if (not Success) then
begin
if fLoop then
begin
- // Record the time we looped. This is used to keep the loops in time. otherwise they speed
+ // we have to loop, so rewind
SetPosition(0);
+ // record the start-time of the current loop, so we can
+ // determine the position in the stream (fTime-fLoopTime) later.
fLoopTime := Time;
end;
Exit;
@@ -695,6 +713,9 @@ begin
fCodecContext^.width, fCodecContext^.height,
PIXEL_FMT_OPENGL, GL_UNSIGNED_BYTE, fAVFrameRGB^.data[0]);
+ if (not fFrameTexValid) then
+ fFrameTexValid := true;
+
{$ifdef DebugFrames}
//frame decode debug display
GoldenRec.Spawn(200, 35, 1, 16, 0, -1, ColoredStar, $ffff00);
@@ -738,7 +759,9 @@ begin
acoLetterBox: begin
ScaledVideoWidth := RenderW;
ScaledVideoHeight := RenderH * ScreenAspect/fAspect;
- end;
+ end
+ else
+ raise Exception.Create('Unhandled aspect correction!');
end;
// center video
@@ -858,6 +881,14 @@ procedure TVideoPlayback_FFmpeg.Stop;
begin
end;
+{**
+ * Sets the stream's position.
+ * The stream is set to the first keyframe with timestamp <= Time.
+ * Note that fTime is set to Time no matter if the actual position seeked to is
+ * at Time or the time of a preceding keyframe. fTime will be updated to the
+ * actual frame time when GetFrame() is called the next time.
+ * @param Time new position in seconds
+ *}
procedure TVideoPlayback_FFmpeg.SetPosition(Time: real);
var
SeekFlags: integer;
@@ -871,13 +902,18 @@ begin
// TODO: handle fLoop-times
//Time := Time mod VideoDuration;
- // backward seeking might fail without AVSEEK_FLAG_BACKWARD
- SeekFlags := AVSEEK_FLAG_ANY;
- if (Time < fTime) then
- SeekFlags := SeekFlags or AVSEEK_FLAG_BACKWARD;
+ // Do not use the AVSEEK_FLAG_ANY here. It will seek to any frame, even
+ // non keyframes (P-/B-frames). It will produce corrupted video frames as
+ // FFmpeg does not use the information of the preceding I-frame.
+ // The picture might be gray or green until the next keyframe occurs.
+ // Instead seek the first keyframe smaller than the requested time
+ // (AVSEEK_FLAG_BACKWARD). As this can be some seconds earlier than the
+ // requested time, let the sync in GetFrame() do its job.
+ SeekFlags := AVSEEK_FLAG_BACKWARD;
fTime := Time;
fEOF := false;
+ fFrameTexValid := false;
if (av_seek_frame(fFormatContext, fStreamIndex, Floor(Time/fTimeBase), SeekFlags) < 0) then
begin
@@ -890,7 +926,6 @@ end;
function TVideoPlayback_FFmpeg.GetPosition: real;
begin
- // TODO: return video-position in seconds
Result := fTime;
end;
--
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