diff --git a/audio/out/ao_lavc.c b/audio/out/ao_lavc.c
index 7d31f63ec9..afb021f7a0 100644
--- a/audio/out/ao_lavc.c
+++ b/audio/out/ao_lavc.c
@@ -102,12 +102,14 @@ static int init(struct ao *ao)
         return -1;
     }
 
+    pthread_mutex_lock(&ao->encode_lavc_ctx->lock);
+
     ac->stream = encode_lavc_alloc_stream(ao->encode_lavc_ctx,
                                           AVMEDIA_TYPE_AUDIO);
 
     if (!ac->stream) {
         MP_ERR(ao, "could not get a new audio stream\n");
-        return -1;
+        goto fail;
     }
 
     codec = encode_lavc_get_codec(ao->encode_lavc_ctx, ac->stream);
@@ -126,7 +128,7 @@ static int init(struct ao *ao)
     struct mp_chmap_sel sel = {0};
     mp_chmap_sel_add_any(&sel);
     if (!ao_chmap_sel_adjust(ao, &sel, &ao->channels))
-        return -1;
+        goto fail;
     mp_chmap_reorder_to_lavc(&ao->channels);
     ac->stream->codec->channels = ao->channels.num;
     ac->stream->codec->channel_layout = mp_chmap_to_lavc(&ao->channels);
@@ -140,7 +142,7 @@ static int init(struct ao *ao)
     ac->stream->codec->bits_per_raw_sample = ac->sample_size * 8;
 
     if (encode_lavc_open_codec(ao->encode_lavc_ctx, ac->stream) < 0)
-        return -1;
+        goto fail;
 
     ac->pcmhack = 0;
     if (ac->stream->codec->frame_size <= 1)
@@ -169,7 +171,12 @@ static int init(struct ao *ao)
 
     ao->untimed = true;
 
+    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
     return 0;
+
+fail:
+    pthread_mutex_unlock(&ao->encode_lavc_ctx->lock);
+    return -1;
 }
 
 // close audio device
@@ -179,8 +186,11 @@ static void uninit(struct ao *ao, bool cut_audio)
     struct priv *ac = ao->priv;
     struct encode_lavc_context *ectx = ao->encode_lavc_ctx;
 
+    pthread_mutex_lock(&ectx->lock);
+
     if (!encode_lavc_start(ectx)) {
         MP_WARN(ao, "not even ready to encode audio at end -> dropped");
+        pthread_mutex_unlock(&ectx->lock);
         return;
     }
 
@@ -192,7 +202,7 @@ static void uninit(struct ao *ao, bool cut_audio)
         while (encode(ao, outpts, NULL) > 0) ;
     }
 
-    ao->priv = NULL;
+    pthread_mutex_unlock(&ectx->lock);
 }
 
 // return: how many bytes can be played without blocking
@@ -323,8 +333,11 @@ static int play(struct ao *ao, void **data, int samples, int flags)
     double nextpts;
     double outpts;
 
+    pthread_mutex_lock(&ectx->lock);
+
     if (!encode_lavc_start(ectx)) {
         MP_WARN(ao, "not ready yet for encoding audio\n");
+        pthread_mutex_unlock(&ectx->lock);
         return 0;
     }
 
@@ -354,6 +367,7 @@ static int play(struct ao *ao, void **data, int samples, int flags)
             talloc_free(tmp);
         }
 
+        pthread_mutex_unlock(&ectx->lock);
         return FFMIN(written, samples);
     }
 
@@ -444,6 +458,7 @@ static int play(struct ao *ao, void **data, int samples, int flags)
             ectx->next_in_pts = nextpts;
     }
 
+    pthread_mutex_unlock(&ectx->lock);
     return bufpos;
 }
 
diff --git a/common/encode_lavc.c b/common/encode_lavc.c
index 5f9e2a0390..5d9853673b 100644
--- a/common/encode_lavc.c
+++ b/common/encode_lavc.c
@@ -103,6 +103,15 @@ static bool value_has_flag(const char *value, const char *flag)
         return val; \
     }
 
+#define CHECK_FAIL_UNLOCK(ctx, val) \
+    if (ctx && (ctx->failed || ctx->finished)) { \
+        MP_ERR(ctx, \
+               "Called a function on a %s encoding context. Bailing out.\n", \
+               ctx->failed ? "failed" : "finished"); \
+        pthread_mutex_unlock(&ctx->lock); \
+        return val; \
+    }
+
 int encode_lavc_available(struct encode_lavc_context *ctx)
 {
     CHECK_FAIL(ctx, 0);
@@ -134,6 +143,7 @@ struct encode_lavc_context *encode_lavc_init(struct encode_output_conf *options,
         mp_msg_force_stderr(global, true);
 
     ctx = talloc_zero(NULL, struct encode_lavc_context);
+    pthread_mutex_init(&ctx->lock, NULL);
     ctx->log = mp_log_new(ctx, global->log, "encode-lavc");
     ctx->global = global;
     encode_lavc_discontinuity(ctx);
@@ -309,6 +319,7 @@ void encode_lavc_free(struct encode_lavc_context *ctx)
         encode_lavc_fail(ctx,
                          "called encode_lavc_free without encode_lavc_finish\n");
 
+    pthread_mutex_destroy(&ctx->lock);
     talloc_free(ctx);
 }
 
@@ -383,14 +394,18 @@ void encode_lavc_finish(struct encode_lavc_context *ctx)
 
 void encode_lavc_set_video_fps(struct encode_lavc_context *ctx, float fps)
 {
+    pthread_mutex_lock(&ctx->lock);
     ctx->vo_fps = fps;
+    pthread_mutex_unlock(&ctx->lock);
 }
 
 void encode_lavc_set_audio_pts(struct encode_lavc_context *ctx, double pts)
 {
     if (ctx) {
+        pthread_mutex_lock(&ctx->lock);
         ctx->last_audio_in_pts = pts;
         ctx->samples_since_last_pts = 0;
+        pthread_mutex_unlock(&ctx->lock);
     }
 }
 
@@ -780,11 +795,15 @@ void encode_lavc_discontinuity(struct encode_lavc_context *ctx)
     if (!ctx)
         return;
 
-    CHECK_FAIL(ctx, );
+    pthread_mutex_lock(&ctx->lock);
+
+    CHECK_FAIL_UNLOCK(ctx, );
 
     ctx->audio_pts_offset = MP_NOPTS_VALUE;
     ctx->last_video_in_pts = MP_NOPTS_VALUE;
     ctx->discontinuity_pts_offset = MP_NOPTS_VALUE;
+
+    pthread_mutex_unlock(&ctx->lock);
 }
 
 static void encode_lavc_printoptions(struct mp_log *log, void *obj,
@@ -1013,7 +1032,9 @@ int encode_lavc_getstatus(struct encode_lavc_context *ctx,
     if (!ctx)
         return -1;
 
-    CHECK_FAIL(ctx, -1);
+    pthread_mutex_lock(&ctx->lock);
+
+    CHECK_FAIL_UNLOCK(ctx, -1);
 
     minutes = (now - ctx->t0) / 60.0 * (1 - f) / f;
     megabytes = ctx->avc->pb ? (avio_size(ctx->avc->pb) / 1048576.0 / f) : 0;
@@ -1029,12 +1050,16 @@ int encode_lavc_getstatus(struct encode_lavc_context *ctx,
         snprintf(buf, bufsize, "{%.1fmin %.1fMB}",
                  minutes, megabytes);
     buf[bufsize - 1] = 0;
+
+    pthread_mutex_unlock(&ctx->lock);
     return 0;
 }
 
 void encode_lavc_expect_stream(struct encode_lavc_context *ctx, int mt)
 {
-    CHECK_FAIL(ctx, );
+    pthread_mutex_lock(&ctx->lock);
+
+    CHECK_FAIL_UNLOCK(ctx, );
 
     switch (mt) {
     case AVMEDIA_TYPE_VIDEO:
@@ -1044,11 +1069,18 @@ void encode_lavc_expect_stream(struct encode_lavc_context *ctx, int mt)
         ctx->expect_audio = true;
         break;
     }
+
+    pthread_mutex_unlock(&ctx->lock);
 }
 
 bool encode_lavc_didfail(struct encode_lavc_context *ctx)
 {
-    return ctx && ctx->failed;
+    if (!ctx)
+        return false;
+    pthread_mutex_lock(&ctx->lock);
+    bool fail = ctx && ctx->failed;
+    pthread_mutex_unlock(&ctx->lock);
+    return fail;
 }
 
 void encode_lavc_fail(struct encode_lavc_context *ctx, const char *format, ...)
diff --git a/common/encode_lavc.h b/common/encode_lavc.h
index deaf42b684..af7f4fba3d 100644
--- a/common/encode_lavc.h
+++ b/common/encode_lavc.h
@@ -22,6 +22,8 @@
 #ifndef MPLAYER_ENCODE_LAVC_H
 #define MPLAYER_ENCODE_LAVC_H
 
+#include <pthread.h>
+
 #include <libavcodec/avcodec.h>
 #include <libavformat/avformat.h>
 #include <libavutil/avstring.h>
@@ -37,6 +39,11 @@ struct encode_lavc_context {
     struct encode_output_conf *options;
     struct mp_log *log;
 
+    // All entry points must be guarded with the lock. Functions called by
+    // the playback core lock this automatically, but ao_lavc.c and vo_lavc.c
+    // must lock manually before accessing state.
+    pthread_mutex_t lock;
+
     float vo_fps;
 
     // these are processed from the options
diff --git a/video/out/vo_lavc.c b/video/out/vo_lavc.c
index e96556b1e8..b5176ebcb4 100644
--- a/video/out/vo_lavc.c
+++ b/video/out/vo_lavc.c
@@ -74,19 +74,21 @@ static int preinit(struct vo *vo)
     return 0;
 }
 
-static void draw_image(struct vo *vo, mp_image_t *mpi);
+static void draw_image_unlocked(struct vo *vo, mp_image_t *mpi);
 static void uninit(struct vo *vo)
 {
     struct priv *vc = vo->priv;
     if (!vc)
         return;
 
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
+
     if (vc->lastipts >= 0 && vc->stream)
-        draw_image(vo, NULL);
+        draw_image_unlocked(vo, NULL);
 
     mp_image_unrefp(&vc->lastimg);
 
-    vo->priv = NULL;
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
 }
 
 static int reconfig(struct vo *vo, struct mp_image_params *params, int flags)
@@ -101,6 +103,8 @@ static int reconfig(struct vo *vo, struct mp_image_params *params, int flags)
     if (!vc)
         return -1;
 
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
+
     display_aspect_ratio.num = params->d_w;
     display_aspect_ratio.den = params->d_h;
     image_aspect_ratio.num = width;
@@ -123,7 +127,7 @@ static int reconfig(struct vo *vo, struct mp_image_params *params, int flags)
                        vc->stream->codec->sample_aspect_ratio.den,
                        aspect.num, aspect.den);
             }
-            return 0;
+            goto done;
         }
 
         /* FIXME Is it possible with raw video? */
@@ -168,9 +172,12 @@ static int reconfig(struct vo *vo, struct mp_image_params *params, int flags)
 
     mp_image_unrefp(&vc->lastimg);
 
+done:
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
     return 0;
 
 error:
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
     uninit(vo);
     return -1;
 }
@@ -182,14 +189,12 @@ static int query_format(struct vo *vo, uint32_t format)
     if (!vo->encode_lavc_ctx)
         return 0;
 
-    if (!encode_lavc_supports_pixfmt(vo->encode_lavc_ctx, pix_fmt))
-        return 0;
-
-    return
-        VFCAP_CSP_SUPPORTED |
-            // we can do it
-        VFCAP_CSP_SUPPORTED_BY_HW;
-            // we don't convert colorspaces here
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
+    int flags = 0;
+    if (encode_lavc_supports_pixfmt(vo->encode_lavc_ctx, pix_fmt))
+        flags = VFCAP_CSP_SUPPORTED | VFCAP_CSP_SUPPORTED_BY_HW;
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
+    return flags;
 }
 
 static void write_packet(struct vo *vo, int size, AVPacket *packet)
@@ -272,7 +277,7 @@ static int encode_video(struct vo *vo, AVFrame *frame, AVPacket *packet)
     }
 }
 
-static void draw_image(struct vo *vo, mp_image_t *mpi)
+static void draw_image_unlocked(struct vo *vo, mp_image_t *mpi)
 {
     struct priv *vc = vo->priv;
     struct encode_lavc_context *ectx = vo->encode_lavc_ctx;
@@ -479,6 +484,13 @@ static void draw_image(struct vo *vo, mp_image_t *mpi)
     }
 }
 
+static void draw_image(struct vo *vo, mp_image_t *mpi)
+{
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
+    draw_image_unlocked(vo, mpi);
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
+}
+
 static void flip_page_timed(struct vo *vo, int64_t pts_us, int duration)
 {
 }
@@ -487,6 +499,8 @@ static void draw_osd(struct vo *vo, struct osd_state *osd)
 {
     struct priv *vc = vo->priv;
 
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
+
     if (vc->lastimg && vc->lastimg_wants_osd && vo->params) {
         struct mp_osd_res dim = osd_res_from_image_params(vo->params);
 
@@ -495,11 +509,15 @@ static void draw_osd(struct vo *vo, struct osd_state *osd)
         osd_draw_on_image(osd, dim, osd_get_vo_pts(osd), OSD_DRAW_SUB_ONLY,
                           vc->lastimg);
     }
+
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
 }
 
 static int control(struct vo *vo, uint32_t request, void *data)
 {
     struct priv *vc = vo->priv;
+    int r = VO_NOTIMPL;
+    pthread_mutex_lock(&vo->encode_lavc_ctx->lock);
     switch (request) {
     case VOCTRL_SET_YUV_COLORSPACE:
         vc->colorspace = *(struct mp_csp_details *)data;
@@ -509,12 +527,15 @@ static int control(struct vo *vo, uint32_t request, void *data)
             vc->colorspace.format = encode_lavc_get_csp(vo->encode_lavc_ctx, vc->stream);
             vc->colorspace.levels_out = encode_lavc_get_csp_levels(vo->encode_lavc_ctx, vc->stream);
         }
-        return 1;
+        r = 1;
+        break;
     case VOCTRL_GET_YUV_COLORSPACE:
         *(struct mp_csp_details *)data = vc->colorspace;
-        return 1;
+        r = 1;
+        break;
     }
-    return VO_NOTIMPL;
+    pthread_mutex_unlock(&vo->encode_lavc_ctx->lock);
+    return r;
 }
 
 const struct vo_driver video_out_lavc = {