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Validate final FFmpeg hardening stack together #103

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Validate final FFmpeg hardening stack together #103

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29475c9
Audit: combine final FFmpeg hardening stack
Blackspirits Sep 13, 2026
fba72f8
Audit: preserve final FFmpeg hardening rationale
Blackspirits Sep 13, 2026
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52 changes: 48 additions & 4 deletions src/ui/Logic/VideoPlayers/Ffmpeg/FfmpegPlayer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -935,6 +935,7 @@ private void VideoLoop()
var swsSourceFormat = AVPixelFormat.AV_PIX_FMT_NONE;
var outputWidth = 0;
var outputHeight = 0;
VideoFrame? lastDropped = null; // detached from the queue while seeking; must be returned on every exit

try
{
Expand All @@ -950,9 +951,9 @@ private void VideoLoop()
: 1.0 / 25.0;

var serial = -1;
var minimumReplaySerial = -1;
var dropUntil = -1.0;
var presentedForSerial = false;
VideoFrame? lastDropped = null; // kept so a target past the last picture still shows something

while (!_closing)
{
Expand All @@ -961,6 +962,19 @@ private void VideoLoop()
continue;
}

if (minimumReplaySerial >= 0 && entry.Serial < minimumReplaySerial)
{
var stalePacket = entry.Packet;
if (stalePacket != null)
{
ffmpeg.av_packet_free(&stalePacket);
}

continue;
}

minimumReplaySerial = -1;

if (entry.Serial != serial)
{
ffmpeg.avcodec_flush_buffers(codec);
Expand All @@ -985,6 +999,7 @@ private void VideoLoop()
// The hardware decoder rejected the stream - retry it in software.
codec = FallBackToSoftware(codec, stream, sendResult, ref hardware);
serial = -1;
minimumReplaySerial = RequestHardwareFallbackReplay();
}

continue;
Expand Down Expand Up @@ -1092,7 +1107,7 @@ private void VideoLoop()
// the key frame.
codec = FallBackToSoftware(codec, stream, 0, ref hardware);
serial = -1;
Seek(Position);
minimumReplaySerial = RequestHardwareFallbackReplay();
continue;
}

Expand Down Expand Up @@ -1124,6 +1139,8 @@ private void VideoLoop()
}
finally
{
_videoFrames.Return(lastDropped);

if (sws != null)
{
ffmpeg.sws_freeContext(sws);
Expand All @@ -1146,6 +1163,22 @@ private void VideoLoop()
}
}

private int RequestHardwareFallbackReplay()
{
var target = Position;
Seek(target);

// Do not let already-demuxed packets from the failed hardware serial feed the fresh
// software decoder before the demux thread performs the seek. A user seek that races
// with this one has a higher serial and is also safe to accept.
_videoFrames.Flush();
_presentWake.Set();
lock (_seekLock)
{
return _requestedSerial;
}
}

private AVCodecContext* FallBackToSoftware(AVCodecContext* codec, AVStream* stream, int error, ref bool hardware)
{
var reason = error < 0 ? FfmpegLibraries.ErrorText(error) : "picture transfer failed";
Expand Down Expand Up @@ -1296,7 +1329,7 @@ private static bool SupportsHardwareDevice(AVCodec* decoder, AVHWDeviceType devi
/// is attached; the caller can tell by <c>hw_device_ctx</c> being set. Any hardware setup
/// failure silently means software.
/// </summary>
private AVCodecContext* OpenDecoder(AVStream* stream, bool hardware = false)
private AVCodecContext* OpenDecoder(AVStream* stream, bool hardware = false, int hardwareStartIndex = 0)
{
var decoder = ffmpeg.avcodec_find_decoder(stream->codecpar->codec_id);
if (decoder == null)
Expand All @@ -1320,10 +1353,12 @@ private static bool SupportsHardwareDevice(AVCodec* decoder, AVHWDeviceType devi
codec->pkt_timebase = stream->time_base;
codec->thread_count = 0; // auto

var selectedHardwareIndex = -1;
if (hardware && stream->codecpar->codec_type == AVMediaType.AVMEDIA_TYPE_VIDEO)
{
foreach (var deviceType in HardwareDeviceTypes)
for (var i = hardwareStartIndex; i < HardwareDeviceTypes.Length; i++)
{
var deviceType = HardwareDeviceTypes[i];
if (!SupportsHardwareDevice(decoder, deviceType))
{
continue;
Expand All @@ -1346,13 +1381,22 @@ private static bool SupportsHardwareDevice(AVCodec* decoder, AVHWDeviceType devi

codec->hw_device_ctx = device; // freed with the codec context
codec->get_format = GetHardwareFormatDelegate;
selectedHardwareIndex = i;
break;
}
}

result = ffmpeg.avcodec_open2(codec, decoder, null);
if (result < 0)
{
if (hardware && selectedHardwareIndex >= 0)
{
var deviceName = HardwareDeviceName(codec);
Se.LogError($"ffmpeg player: {deviceName} decoder open failed for {ffmpeg.avcodec_get_name(stream->codecpar->codec_id)} ({FfmpegLibraries.ErrorText(result)}), trying the next hardware decoder or software");
ffmpeg.avcodec_free_context(&codec);
return OpenDecoder(stream, hardware: true, hardwareStartIndex: selectedHardwareIndex + 1);
}

ffmpeg.avcodec_free_context(&codec);
throw new InvalidOperationException($"avcodec_open2: {FfmpegLibraries.ErrorText(result)}");
}
Expand Down
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