ffmpeg采集帧出错不退出的补丁

在ffmpeg2.81.11和ffmpeg3.0.7上试验。
ffmpeg没有FFERROR_REDO常量定义，但ffmpeg3.0.7上有。

diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c

old mode 100644

new mode 100755

index ddf331d..7b4a826

--- a/libavdevice/v4l2.c

+++ b/libavdevice/v4l2.c

@@ -79,6 +79,7 @@  struct video_data {

     int buffers;

     volatile int buffers_queued;

+    int buffers_ignore;

     void **buf_start;

     unsigned int *buf_len;

     char *standard;

@@ -519,7 +520,9 @@  static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)

         av_log(ctx, AV_LOG_WARNING,

                "Dequeued v4l2 buffer contains corrupted data (%d bytes).\n",

                buf.bytesused);

-        buf.bytesused = 0;

+        s->buffers_ignore = 8;

+        enqueue_buffer(s, &buf);

+        return FFERROR_REDO;

     } else

 #endif

     {

@@ -529,14 +532,28 @@  static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt)

             s->frame_size = buf.bytesused;

         if (s->frame_size > 0 && buf.bytesused != s->frame_size) {

-            av_log(ctx, AV_LOG_ERROR,

+            av_log(ctx, AV_LOG_WARNING,

                    "Dequeued v4l2 buffer contains %d bytes, but %d were expected. Flags: 0x%08X.\n",

                    buf.bytesused, s->frame_size, buf.flags);

+            s->buffers_ignore = 8;

             enqueue_buffer(s, &buf);

-            return AVERROR_INVALIDDATA;

+            return FFERROR_REDO;

         }

     }

+

+    /* if we just encounted some corrupted buffers then we ignore the next few

+     * legitimate buffers because they can arrive at irregular intervals, causing

+     * the timestamps of the input and output streams to be out-of-sync and FFmpeg

+     * to continually emit warnings. */

+    if (s->buffers_ignore) {

+        av_log(ctx, AV_LOG_WARNING,

+               "Ignoring dequeued v4l2 buffer due to earlier corruption.\n");

+        s->buffers_ignore --;

+        enqueue_buffer(s, &buf);

+        return FFERROR_REDO;

+    }

+

     /* 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, fall back on copying data */

@@ -608,6 +625,7 @@  static int mmap_start(AVFormatContext *ctx)

         }

     }

     s->buffers_queued = s->buffers;

+    s->buffers_ignore = 0;

     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

     if (v4l2_ioctl(s->fd, VIDIOC_STREAMON, &type) < 0) {

参考自https://patchwork.kernel.org/patch/9324933/