[FFmpeg-devel] [PATCH v8 2/3] libavdevice/avfoundation.m: Replace mutex-based concurrency handling in avfoundation.m by a thread-safe fifo queue with maximum length

[Romain Beauxis <toots@rastageeks.org>]

* Use a CMSimpleQueueEnqueue with maximum length to queue and process incoming audio and video frames.
* Log avfoundation errors.
* Use AVERROR_EXTERNAL instead of AVERROR(EIO) in avfoundation errors.

Signed-off-by: Romain Beauxis <toots@rastageeks.org>
—
[Sorry for the noise but an issue came up with the previous set]

This is the second patch of a series of 3 that fix, cleanup and enhance the
avfoundation implementation for libavdevice.

These patches come from an actual user-facing application relying on
libavdevice’s implementation of avfoundation audio input. Without them,
Avfoundation is practically unusable as it will:
* Refuse to process certain specific audio input format that are actually
returned by the OS for some users (packed PCM audio)
* Drop audio frames, resulting in corrupted audio input. This might have been
unnoticed with video frames but this makes avfoundation essentially unusable
for audio.

The patches are now being included in our production build so they are tested
and usable in production.

Changelog for this patch:
* v2: None
* v3: None
* v4: None
* v5: Fix indentation/wrapping
* v6: None
* v7: Removed use of kAudioConverterPropertyCalculateOutputBufferSize
to calculate output buffer size. The calculation is trivial and this call was 
randomly failing for no reason
* v8: Fix memory leak when video or audio queue is full

libavdevice/avfoundation.m | 194 +++++++++++++++++++------------------
1 file changed, 100 insertions(+), 94 deletions(-)

diff --git a/libavdevice/avfoundation.m b/libavdevice/avfoundation.m
index 738cd93375..36f9fdc53d 100644
--- a/libavdevice/avfoundation.m
+++ b/libavdevice/avfoundation.m
@@ -26,7 +26,7 @@
 */

#import <AVFoundation/AVFoundation.h>
-#include <pthread.h>
+#import <CoreMedia/CoreMedia.h>

#include "libavutil/channel_layout.h"
#include "libavutil/pixdesc.h"
@@ -39,6 +39,11 @@
#include "libavutil/imgutils.h"
#include "avdevice.h"

+#define av_log_avfoundation_error(s, str, err) \
+   av_log(s, AV_LOG_ERROR, "Avfoundation: %s, %s\n", str, \
+     [[[NSError errorWithDomain:NSOSStatusErrorDomain code:err userInfo:nil] localizedDescription] UTF8String] \
+  )
+
static const int avf_time_base = 1000000;

static const AVRational avf_time_base_q = {
@@ -80,13 +85,12 @@
    { AV_PIX_FMT_NONE, 0 }
};

+#define MAX_QUEUED_FRAMES 10
+
typedef struct
{
    AVClass*        class;

-    int             frames_captured;
-    int             audio_frames_captured;
-    pthread_mutex_t frame_lock;
    id              avf_delegate;
    id              avf_audio_delegate;

@@ -122,8 +126,8 @@
    AVCaptureSession         *capture_session;
    AVCaptureVideoDataOutput *video_output;
    AVCaptureAudioDataOutput *audio_output;
-    CMSampleBufferRef         current_frame;
-    CMSampleBufferRef         current_audio_frame;
+    CMSimpleQueueRef          audio_frames_queue;
+    CMSimpleQueueRef          video_frames_queue;

    AVCaptureDevice          *observed_device;
#if !TARGET_OS_IPHONE && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
@@ -132,16 +136,6 @@
    int                      observed_quit;
} AVFContext;

-static void lock_frames(AVFContext* ctx)
-{
-    pthread_mutex_lock(&ctx->frame_lock);
-}
-
-static void unlock_frames(AVFContext* ctx)
-{
-    pthread_mutex_unlock(&ctx->frame_lock);
-}
-
/** FrameReciever class - delegate for AVCaptureSession
 */
@interface AVFFrameReceiver : NSObject
@@ -219,17 +213,13 @@ - (void)  captureOutput:(AVCaptureOutput *)captureOutput
  didOutputSampleBuffer:(CMSampleBufferRef)videoFrame
         fromConnection:(AVCaptureConnection *)connection
{
-    lock_frames(_context);
+    OSStatus ret = CMSimpleQueueEnqueue(_context->video_frames_queue, videoFrame);

-    if (_context->current_frame != nil) {
-        CFRelease(_context->current_frame);
+    if (ret != noErr) {
+      av_log_avfoundation_error(_context, "Error while queueing video frame", ret);
    }

-    _context->current_frame = (CMSampleBufferRef)CFRetain(videoFrame);
-
-    unlock_frames(_context);
-
-    ++_context->frames_captured;
+    CFRetain(videoFrame);
}

@end
@@ -263,17 +253,13 @@ - (void)  captureOutput:(AVCaptureOutput *)captureOutput
  didOutputSampleBuffer:(CMSampleBufferRef)audioFrame
         fromConnection:(AVCaptureConnection *)connection
{
-    lock_frames(_context);
+    OSStatus ret = CMSimpleQueueEnqueue(_context->audio_frames_queue, audioFrame);

-    if (_context->current_audio_frame != nil) {
-        CFRelease(_context->current_audio_frame);
+    if (ret != noErr) {
+      av_log_avfoundation_error(_context, "Error while queueing audio frame", ret);
    }

-    _context->current_audio_frame = (CMSampleBufferRef)CFRetain(audioFrame);
-
-    unlock_frames(_context);
-
-    ++_context->audio_frames_captured;
+    CFRetain(audioFrame);
}

@end
@@ -288,6 +274,30 @@ static void destroy_context(AVFContext* ctx)
    [ctx->avf_delegate    release];
    [ctx->avf_audio_delegate release];

+    CMSampleBufferRef frame;
+
+    if (ctx->video_frames_queue) {
+        frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->video_frames_queue);
+        while (frame) {
+          CFRelease(frame);
+          frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->video_frames_queue);
+        }
+
+        CFRelease(ctx->video_frames_queue);
+        ctx->video_frames_queue = NULL;
+    }
+
+    if (ctx->audio_frames_queue) {
+        frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->audio_frames_queue);
+        while (frame) {
+          CFRelease(frame);
+          frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->audio_frames_queue);
+        }
+
+        CFRelease(ctx->audio_frames_queue);
+        ctx->audio_frames_queue = NULL;
+    }
+
    ctx->capture_session = NULL;
    ctx->video_output    = NULL;
    ctx->audio_output    = NULL;
@@ -298,12 +308,6 @@ static void destroy_context(AVFContext* ctx)
      AudioConverterDispose(ctx->audio_converter);
      ctx->audio_converter = NULL;
    }
-
-    pthread_mutex_destroy(&ctx->frame_lock);
-
-    if (ctx->current_frame) {
-        CFRelease(ctx->current_frame);
-    }
}

static void parse_device_name(AVFormatContext *s)
@@ -631,18 +635,18 @@ static int get_video_config(AVFormatContext *s)
    }

    // Take stream info from the first frame.
-    while (ctx->frames_captured < 1) {
+    while (CMSimpleQueueGetCount(ctx->video_frames_queue) < 1) {
        CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.1, YES);
    }

-    lock_frames(ctx);
+    CMSampleBufferRef frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->video_frames_queue);

    ctx->video_stream_index = stream->index;

    avpriv_set_pts_info(stream, 64, 1, avf_time_base);

-    image_buffer = CMSampleBufferGetImageBuffer(ctx->current_frame);
-    block_buffer = CMSampleBufferGetDataBuffer(ctx->current_frame);
+    image_buffer = CMSampleBufferGetImageBuffer(frame);
+    block_buffer = CMSampleBufferGetDataBuffer(frame);

    if (image_buffer) {
        image_buffer_size = CVImageBufferGetEncodedSize(image_buffer);
@@ -658,10 +662,7 @@ static int get_video_config(AVFormatContext *s)
        stream->codecpar->format     = ctx->pixel_format;
    }

-    CFRelease(ctx->current_frame);
-    ctx->current_frame = nil;
-
-    unlock_frames(ctx);
+    CFRelease(frame);

    return 0;
}
@@ -681,27 +682,27 @@ static int get_audio_config(AVFormatContext *s)
    }

    // Take stream info from the first frame.
-    while (ctx->audio_frames_captured < 1) {
+    while (CMSimpleQueueGetCount(ctx->audio_frames_queue) < 1) {
        CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.1, YES);
    }

-    lock_frames(ctx);
+    CMSampleBufferRef frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->audio_frames_queue);

    ctx->audio_stream_index = stream->index;

    avpriv_set_pts_info(stream, 64, 1, avf_time_base);

-    format_desc = CMSampleBufferGetFormatDescription(ctx->current_audio_frame);
+    format_desc = CMSampleBufferGetFormatDescription(frame);
    const AudioStreamBasicDescription *input_format = CMAudioFormatDescriptionGetStreamBasicDescription(format_desc);

    if (!input_format) {
-        unlock_frames(ctx);
+        CFRelease(frame);
        av_log(s, AV_LOG_ERROR, "audio format not available\n");
        return 1;
    }

    if (input_format->mFormatID != kAudioFormatLinearPCM) {
-        unlock_frames(ctx);
+        CFRelease(frame);
        av_log(s, AV_LOG_ERROR, "only PCM audio format are supported at the moment\n");
        return 1;
    }
@@ -781,16 +782,13 @@ static int get_audio_config(AVFormatContext *s)
    if (must_convert) {
        OSStatus ret = AudioConverterNew(input_format, &output_format, &ctx->audio_converter);
        if (ret != noErr) {
-            unlock_frames(ctx);
-            av_log(s, AV_LOG_ERROR, "Error while allocating audio converter\n");
+            CFRelease(frame);
+            av_log_avfoundation_error(s, "error while creating audio converter", ret);
            return 1;
        }
    }

-    CFRelease(ctx->current_audio_frame);
-    ctx->current_audio_frame = nil;
-
-    unlock_frames(ctx);
+    CFRelease(frame);

    return 0;
}
@@ -808,8 +806,6 @@ static int avf_read_header(AVFormatContext *s)

    ctx->num_video_devices = [devices count] + [devices_muxed count];

-    pthread_mutex_init(&ctx->frame_lock, NULL);
-
#if !TARGET_OS_IPHONE && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
    CGGetActiveDisplayList(0, NULL, &num_screens);
#endif
@@ -1010,6 +1006,21 @@ static int avf_read_header(AVFormatContext *s)
    // Initialize capture session
    ctx->capture_session = [[AVCaptureSession alloc] init];

+    OSStatus ret;
+    ret = CMSimpleQueueCreate(kCFAllocatorDefault, MAX_QUEUED_FRAMES, &ctx->video_frames_queue);
+
+    if (ret != noErr) {
+        av_log_avfoundation_error(s, "error while creating frame queue", ret);
+        goto fail;
+    }
+
+    ret = CMSimpleQueueCreate(kCFAllocatorDefault, MAX_QUEUED_FRAMES, &ctx->audio_frames_queue);
+
+    if (ret != noErr) {
+        av_log_avfoundation_error(s, "error while creating frame queue", ret);
+        goto fail;
+    }
+
    if (video_device && add_video_device(s, video_device)) {
        goto fail;
    }
@@ -1039,7 +1050,8 @@ static int avf_read_header(AVFormatContext *s)
fail:
    [pool release];
    destroy_context(ctx);
-    return AVERROR(EIO);
+    av_log(s, AV_LOG_ERROR, "Error while opening AVfoundation capture session\n");
+    return AVERROR_EXTERNAL;
}

static int copy_cvpixelbuffer(AVFormatContext *s,
@@ -1088,38 +1100,35 @@ static int copy_cvpixelbuffer(AVFormatContext *s,
static int avf_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    OSStatus ret;
+    int status;
    AVFContext* ctx = (AVFContext*)s->priv_data;

    do {
-        CVImageBufferRef image_buffer;
-        CMBlockBufferRef block_buffer;
-        lock_frames(ctx);
-
-        if (ctx->current_frame != nil) {
-            int status;
+        if (1 <= CMSimpleQueueGetCount(ctx->video_frames_queue)) {
            int length = 0;
-
-            image_buffer = CMSampleBufferGetImageBuffer(ctx->current_frame);
-            block_buffer = CMSampleBufferGetDataBuffer(ctx->current_frame);
+            CMSampleBufferRef video_frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->video_frames_queue);
+            CVImageBufferRef image_buffer = CMSampleBufferGetImageBuffer(video_frame);;
+            CMBlockBufferRef block_buffer = CMSampleBufferGetDataBuffer(video_frame);

            if (image_buffer != nil) {
                length = (int)CVPixelBufferGetDataSize(image_buffer);
            } else if (block_buffer != nil) {
                length = (int)CMBlockBufferGetDataLength(block_buffer);
            } else  {
-                unlock_frames(ctx);
+                CFRelease(video_frame);
                return AVERROR(EINVAL);
            }

-            if (av_new_packet(pkt, length) < 0) {
-                unlock_frames(ctx);
-                return AVERROR(EIO);
+            status = av_new_packet(pkt, length);
+            if (status < 0) {
+                CFRelease(video_frame);
+                return status;
            }

            CMItemCount count;
            CMSampleTimingInfo timing_info;

-            if (CMSampleBufferGetOutputSampleTimingInfoArray(ctx->current_frame, 1, &timing_info, &count) == noErr) {
+            if (CMSampleBufferGetOutputSampleTimingInfoArray(video_frame, 1, &timing_info, &count) == noErr) {
                AVRational timebase_q = av_make_q(1, timing_info.presentationTimeStamp.timescale);
                pkt->pts = pkt->dts = av_rescale_q(timing_info.presentationTimeStamp.value, timebase_q, avf_time_base_q);
            }
@@ -1133,18 +1142,18 @@ static int avf_read_packet(AVFormatContext *s, AVPacket *pkt)
                status = 0;
                ret = CMBlockBufferCopyDataBytes(block_buffer, 0, pkt->size, pkt->data);
                if (ret != kCMBlockBufferNoErr) {
-                    status = AVERROR(EIO);
+                    av_log_avfoundation_error(s, "error while copying buffer data", ret);
+                    status = AVERROR_EXTERNAL;
                }
             }
-            CFRelease(ctx->current_frame);
-            ctx->current_frame = nil;
+            CFRelease(video_frame);

            if (status < 0) {
-                unlock_frames(ctx);
                return status;
            }
-        } else if (ctx->current_audio_frame != nil) {
-            CMBlockBufferRef block_buffer = CMSampleBufferGetDataBuffer(ctx->current_audio_frame);
+        } else if (1 <= CMSimpleQueueGetCount(ctx->audio_frames_queue)) {
+            CMSampleBufferRef audio_frame = (CMSampleBufferRef)CMSimpleQueueDequeue(ctx->audio_frames_queue);
+            CMBlockBufferRef block_buffer = CMSampleBufferGetDataBuffer(audio_frame);

            size_t input_size = CMBlockBufferGetDataLength(block_buffer);
            int buffer_size = input_size / ctx->audio_buffers;
@@ -1170,8 +1179,9 @@ static int avf_read_packet(AVFormatContext *s, AVPacket *pkt)

                    if (ret != kCMBlockBufferNoErr) {
                        av_free(input_buffer);
-                        unlock_frames(ctx);
-                        return AVERROR(EIO);
+                        CFRelease(audio_frame);
+                        av_log_avfoundation_error(s, "error while accessing audio buffer data", ret);
+                        return AVERROR_EXTERNAL;
                    }
                }

@@ -1188,23 +1198,25 @@ static int avf_read_packet(AVFormatContext *s, AVPacket *pkt)
                av_free(input_buffer);

                if (ret != noErr) {
-                    unlock_frames(ctx);
-                    return AVERROR(EIO);
+                    CFRelease(audio_frame);
+                    av_log_avfoundation_error(s, "error while converting audio data", ret);
+                    return AVERROR_EXTERNAL;
                }

                pkt->size = output_buffer.mBuffers[0].mDataByteSize;
            } else {
                 ret = CMBlockBufferCopyDataBytes(block_buffer, 0, pkt->size, pkt->data);
                 if (ret != kCMBlockBufferNoErr) {
-                     unlock_frames(ctx);
-                     return AVERROR(EIO);
+                     CFRelease(audio_frame);
+                     av_log_avfoundation_error(s, "error while copying audio data", ret);
+                     return AVERROR_EXTERNAL;
                 }
            }

            CMItemCount count;
            CMSampleTimingInfo timing_info;

-            if (CMSampleBufferGetOutputSampleTimingInfoArray(ctx->current_audio_frame, 1, &timing_info, &count) == noErr) {
+            if (CMSampleBufferGetOutputSampleTimingInfoArray(audio_frame, 1, &timing_info, &count) == noErr) {
                AVRational timebase_q = av_make_q(1, timing_info.presentationTimeStamp.timescale);
                pkt->pts = pkt->dts = av_rescale_q(timing_info.presentationTimeStamp.value, timebase_q, avf_time_base_q);
            }
@@ -1212,21 +1224,15 @@ static int avf_read_packet(AVFormatContext *s, AVPacket *pkt)
            pkt->stream_index  = ctx->audio_stream_index;
            pkt->flags        |= AV_PKT_FLAG_KEY;

-            CFRelease(ctx->current_audio_frame);
-            ctx->current_audio_frame = nil;
-
-            unlock_frames(ctx);
+            CFRelease(audio_frame);
        } else {
            pkt->data = NULL;
-            unlock_frames(ctx);
            if (ctx->observed_quit) {
                return AVERROR_EOF;
            } else {
                return AVERROR(EAGAIN);
            }
        }
-
-        unlock_frames(ctx);
    } while (!pkt->data);

    return 0;
-- 
2.32.0 (Apple Git-132)

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