1 files changed, 75 insertions, 72 deletions

diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
index 6726b0b..14306bd 100644
--- a/libavdevice/v4l2.c
+++ b/libavdevice/v4l2.c
@@ -46,6 +46,7 @@
 #endif
 #include <linux/videodev2.h>
 #endif
+#include "libavutil/atomic.h"
 #include "libavutil/avassert.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/log.h"
@@ -109,9 +110,9 @@ struct video_data {
     int64_t last_time_m;
 
     int buffers;
+    volatile int buffers_queued;
     void **buf_start;
     unsigned int *buf_len;
-    int *buf_dequeued;
     char *standard;
     v4l2_std_id std_id;
     int channel;
@@ -122,9 +123,9 @@ struct video_data {
 };
 
 struct buff_data {
+    struct video_data *s;
     int index;
     int fd;
-    int *buf_dequeued;
 };
 
 struct fmt_map {
@@ -438,11 +439,6 @@ static int mmap_init(AVFormatContext *ctx)
         av_free(s->buf_start);
         return AVERROR(ENOMEM);
     }
-    s->buf_dequeued = av_mallocz(sizeof(int) * s->buffers);
-    if (s->buf_dequeued == NULL) {
-        av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer array\n");
-        return AVERROR(ENOMEM);
-    }
 
     for (i = 0; i < req.count; i++) {
         struct v4l2_buffer buf = {
@@ -477,40 +473,33 @@ static int mmap_init(AVFormatContext *ctx)
     return 0;
 }
 
-static int enqueue_buffer(int fd, int index)
+#if FF_API_DESTRUCT_PACKET
+static void dummy_release_buffer(AVPacket *pkt)
+{
+    av_assert0(0);
+}
+#endif
+
+static void mmap_release_buffer(void *opaque, uint8_t *data)
 {
-    int res;
     struct v4l2_buffer buf = { 0 };
+    int res, fd;
+    struct buff_data *buf_descriptor = opaque;
+    struct video_data *s = buf_descriptor->s;
 
-    buf.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     buf.memory = V4L2_MEMORY_MMAP;
-    buf.index  = index;
+    buf.index = buf_descriptor->index;
+    fd = buf_descriptor->fd;
+    av_free(buf_descriptor);
 
     if (v4l2_ioctl(fd, VIDIOC_QBUF, &buf) < 0) {
         res = AVERROR(errno);
-        av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n", av_err2str(res));
-        return res;
+        av_log(NULL, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF): %s\n",
+               av_err2str(res));
     }
-    return 0;
-}
 
-static void mmap_release_buffer(AVPacket *pkt)
-{
-    struct buff_data *buf_descriptor = pkt->priv;
-
-    if (pkt->data == NULL)
-        return;
-
-    if (buf_descriptor->index == -1) {
-        av_free(pkt->data);
-    } else {
-        if (!enqueue_buffer(buf_descriptor->fd, buf_descriptor->index))
-            buf_descriptor->buf_dequeued[buf_descriptor->index] = 0;
-    }
-    av_free(buf_descriptor);
-
-    pkt->data = NULL;
-    pkt->size = 0;
+    avpriv_atomic_int_add_and_fetch(&s->buffers_queued, 1);
 }
 
 #if HAVE_CLOCK_GETTIME && defined(CLOCK_MONOTONIC)
@@ -580,14 +569,15 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
         .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
         .memory = V4L2_MEMORY_MMAP
     };
-    struct buff_data *buf_descriptor;
-    int res, i, free_buffers;
+    int res;
 
     /* FIXME: Some special treatment might be needed in case of loss of signal... */
     while ((res = v4l2_ioctl(s->fd, VIDIOC_DQBUF, &buf)) < 0 && (errno == EINTR));
     if (res < 0) {
-        if (errno == EAGAIN)
+        if (errno == EAGAIN) {
+            pkt->size = 0;
             return AVERROR(EAGAIN);
+        }
         res = AVERROR(errno);
         av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_DQBUF): %s\n", av_err2str(res));
         return res;
@@ -597,6 +587,9 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
         av_log(ctx, AV_LOG_ERROR, "Invalid buffer index received.\n");
         return AVERROR(EINVAL);
     }
+    avpriv_atomic_int_add_and_fetch(&s->buffers_queued, -1);
+    // always keep at least one buffer queued
+    av_assert0(avpriv_atomic_int_get(&s->buffers_queued) >= 1);
 
     /* CPIA is a compressed format and we don't know the exact number of bytes
      * used by a frame, so set it here as the driver announces it.
@@ -608,50 +601,58 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)
         av_log(ctx, AV_LOG_ERROR,
                "The v4l2 frame is %d bytes, but %d bytes are expected\n",
                buf.bytesused, s->frame_size);
-        enqueue_buffer(s->fd, buf.index);
         return AVERROR_INVALIDDATA;
     }
 
-    buf_descriptor = av_malloc(sizeof(struct buff_data));
-    if (buf_descriptor == NULL) {
-        /* Something went wrong... Since av_malloc() failed, we cannot even
-         * allocate a buffer for memcopying into it
-         */
-        av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
-        res = v4l2_ioctl(s->fd, VIDIOC_QBUF, &buf);
-        return AVERROR(ENOMEM);
-    }
-    buf_descriptor->fd = s->fd;
-    buf_descriptor->buf_dequeued = s->buf_dequeued;
-
-    free_buffers = -1; /* start from -1 because we just dequeued a buffer */
-    for (i = 0; i < s->buffers; i++)
-        if (s->buf_dequeued[i] == 0)
-            free_buffers++;
-
-    if (free_buffers == 0) {
-        if ((res = av_new_packet(pkt, buf.bytesused)) < 0) {
-            enqueue_buffer(s->fd, buf.index);
+    /* Image is at s->buff_start[buf.index] */
+    if (avpriv_atomic_int_get(&s->buffers_queued) == FFMAX(s->buffers / 8, 1)) {
+        /* when we start getting low on queued buffers, fallback to copying data */
+        res = av_new_packet(pkt, buf.bytesused);
+        if (res < 0) {
+            av_log(ctx, AV_LOG_ERROR, "Error allocating a packet.\n");
             return res;
         }
         memcpy(pkt->data, s->buf_start[buf.index], buf.bytesused);
-        enqueue_buffer(s->fd, buf.index);
-        buf_descriptor->index = -1;
+
+        res = v4l2_ioctl(s->fd, VIDIOC_QBUF, &buf);
+        if (res < 0) {
+            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QBUF)\n");
+            av_free_packet(pkt);
+            return AVERROR(errno);
+        }
+        avpriv_atomic_int_add_and_fetch(&s->buffers_queued, 1);
     } else {
-        /* Image is at s->buff_start[buf.index] */
-        pkt->data = s->buf_start[buf.index];
+        struct buff_data *buf_descriptor;
+
+        pkt->data     = s->buf_start[buf.index];
+        pkt->size     = buf.bytesused;
+#if FF_API_DESTRUCT_PACKET
+        pkt->destruct = dummy_release_buffer;
+#endif
+
+        buf_descriptor = av_malloc(sizeof(struct buff_data));
+        if (buf_descriptor == NULL) {
+            /* Something went wrong... Since av_malloc() failed, we cannot even
+             * allocate a buffer for memcpying into it
+             */
+            av_log(ctx, AV_LOG_ERROR, "Failed to allocate a buffer descriptor\n");
+            res = v4l2_ioctl(s->fd, VIDIOC_QBUF, &buf);
+
+            return AVERROR(ENOMEM);
+        }
+        buf_descriptor->fd    = s->fd;
         buf_descriptor->index = buf.index;
-        buf_descriptor->buf_dequeued[buf.index] = 1;
+        buf_descriptor->s     = s;
+
+        pkt->buf = av_buffer_create(pkt->data, pkt->size, mmap_release_buffer,
+                                    buf_descriptor, 0);
+        if (!pkt->buf) {
+            av_freep(&buf_descriptor);
+            return AVERROR(ENOMEM);
+        }
     }
-    pkt->size = buf.bytesused;
-    pkt->priv = buf_descriptor;
-    pkt->destruct = mmap_release_buffer;
     pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec;
-    res = convert_timestamp(ctx, &pkt->pts);
-    if (res < 0) {
-        mmap_release_buffer(pkt);
-        return res;
-    }
+    convert_timestamp(ctx, &pkt->pts);
 
     return s->buf_len[buf.index];
 }
@@ -675,6 +676,7 @@ static int mmap_start(AVFormatContext *ctx)
             return res;
         }
     }
+    s->buffers_queued = s->buffers;
 
     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
     if (v4l2_ioctl(s->fd, VIDIOC_STREAMON, &type) < 0) {
@@ -701,7 +703,6 @@ static void mmap_close(struct video_data *s)
     }
     av_free(s->buf_start);
     av_free(s->buf_len);
-    av_free(s->buf_dequeued);
 }
 
 static int v4l2_set_parameters(AVFormatContext *s1)
@@ -1003,8 +1004,6 @@ static int v4l2_read_packet(AVFormatContext *s1, AVPacket *pkt)
     int res;
 
     av_init_packet(pkt);
-    pkt->data = NULL;
-    pkt->size = 0;
     if ((res = mmap_read_frame(s1, pkt)) < 0) {
         return res;
     }
@@ -1021,6 +1020,10 @@ static int v4l2_read_close(AVFormatContext *s1)
 {
     struct video_data *s = s1->priv_data;
 
+    if (avpriv_atomic_int_get(&s->buffers_queued) != s->buffers)
+        av_log(s1, AV_LOG_WARNING, "Some buffers are still owned by the caller on "
+               "close.\n");
+
     mmap_close(s);
 
     v4l2_close(s->fd);