video: let sh_video->aspect always be container aspect ratio

Now writing -1 to the 'aspect' property resets the video to the auto
aspect ratio. Returning the aspect from the property becomes a bit more
complicated, because we still try to return the container aspect ratio
if no frame has been decoded yet.

mpvcore/command.c

@@ -1478,22 +1478,30 @@ static int mp_property_fps(m_option_t *prop, int action, void *arg,
 static int mp_property_aspect(m_option_t *prop, int action, void *arg,
                               MPContext *mpctx)
 {
+    struct sh_video *sh_video = mpctx->sh_video;
     if (!mpctx->sh_video)
         return M_PROPERTY_UNAVAILABLE;
     switch (action) {
     case M_PROPERTY_SET: {
-        float f = *(float *)arg;
-        if (f < 0.1)
-            f = (float)mpctx->sh_video->disp_w / mpctx->sh_video->disp_h;
-        mpctx->opts->movie_aspect = f;
+        mpctx->opts->movie_aspect = *(float *)arg;
         reinit_video_filters(mpctx);
         mp_force_video_refresh(mpctx);
         return M_PROPERTY_OK;
     }
-    case M_PROPERTY_GET:
-        *(float *)arg = mpctx->sh_video->aspect;
+    case M_PROPERTY_GET: {
+        float aspect = -1;
+        struct mp_image_params *params = sh_video->vf_input;
+        if (params && params->d_w && params->d_h) {
+            aspect = (float)params->d_w / params->d_h;
+        } else if (sh_video->disp_w && sh_video->disp_h) {
+            aspect = (float)sh_video->disp_w / sh_video->disp_h;
+        }
+        if (aspect <= 0)
+            return M_PROPERTY_UNAVAILABLE;
+        *(float *)arg = aspect;
         return M_PROPERTY_OK;
     }
+    }
     return M_PROPERTY_NOT_IMPLEMENTED;
 }
 
@@ -1874,7 +1882,7 @@ static const m_option_t mp_properties[] = {
     { "fps", mp_property_fps, CONF_TYPE_FLOAT,
       0, 0, 0, NULL },
     { "aspect", mp_property_aspect, CONF_TYPE_FLOAT,
-      CONF_RANGE, 0, 10, NULL },
+      CONF_RANGE, -1, 10, NULL },
     M_OPTION_PROPERTY_CUSTOM("vid", mp_property_video),
     { "program", mp_property_program, CONF_TYPE_INT,
       CONF_RANGE, -1, 65535, NULL },

mpvcore/options.c

@@ -497,8 +497,10 @@ const m_option_t mp_opts[] = {
     // scaling:
     {"sws", &sws_flags, CONF_TYPE_INT, 0, 0, 2, NULL},
     {"ssf", (void *) scaler_filter_conf, CONF_TYPE_SUBCONFIG, 0, 0, 0, NULL},
-    OPT_FLOATRANGE("aspect", movie_aspect, 0, 0.1, 10.0),
-    OPT_FLOAT_STORE("no-aspect", movie_aspect, 0, 0),
+    // -1 means auto aspect (prefer container size until aspect change)
+    //  0 means square pixels
+    OPT_FLOATRANGE("aspect", movie_aspect, 0, -1.0, 10.0),
+    OPT_FLOAT_STORE("no-aspect", movie_aspect, 0, 0.0),
 
     OPT_FLAG_CONSTANTS("flip", flip, 0, 0, 1),
 

video/decode/vd.c

@@ -115,12 +115,13 @@ int mpcodecs_reconfig_vo(sh_video_t *sh, const struct mp_image_params *params)
     }
     // time to do aspect ratio corrections...
 
-    if (opts->movie_aspect > -1.0)
-        sh->aspect = opts->movie_aspect;        // cmdline overrides autodetect
-    else if (sh->stream_aspect != 0.0)
-        sh->aspect = sh->stream_aspect;
+    float force_aspect = opts->movie_aspect;
+    if (force_aspect > -1.0 && sh->stream_aspect != 0.0)
+        force_aspect = sh->stream_aspect;
+
+    if (force_aspect >= 0)
+        vf_set_dar(&p.d_w, &p.d_h, p.w, p.h, force_aspect);
 
-    vf_set_dar(&p.d_w, &p.d_h, p.w, p.h, sh->aspect);
     if (abs(p.d_w - p.w) >= 4 || abs(p.d_h - p.h) >= 4) {
         mp_tmsg(MSGT_CPLAYER, MSGL_V, "Aspect ratio is %.2f:1 - "
                 "scaling to correct movie aspect.\n", sh->aspect);

video/decode/vd_lavc.c

@@ -492,8 +492,9 @@ static void update_image_params(sh_video_t *sh, AVFrame *frame)
         // But set it even if the sample aspect did not change, since a
         // resolution change can cause an aspect change even if the
         // _sample_ aspect is unchanged.
-        if (sh->aspect == 0 || ctx->last_sample_aspect_ratio.den)
-            sh->aspect = aspect;
+        float use_aspect = sh->aspect;
+        if (use_aspect == 0 || ctx->last_sample_aspect_ratio.den)
+            use_aspect = aspect;
         ctx->last_sample_aspect_ratio = frame->sample_aspect_ratio;
         sh->disp_w = width;
         sh->disp_h = height;
@@ -501,14 +502,15 @@ static void update_image_params(sh_video_t *sh, AVFrame *frame)
         ctx->pix_fmt = pix_fmt;
         ctx->best_csp = pixfmt2imgfmt(pix_fmt);
 
+        int d_w, d_h;
+        vf_set_dar(&d_w, &d_h, width, height, use_aspect);
+
         ctx->image_params = (struct mp_image_params) {
             .imgfmt = ctx->best_csp,
             .w = width,
             .h = height,
-            // Ideally, we should also set aspect ratio, but we aren't there yet
-            // - so vd.c calculates display size from sh->aspect.
-            .d_w = width,
-            .d_h = height,
+            .d_w = d_w,
+            .d_h = d_h,
             .colorspace = avcol_spc_to_mp_csp(ctx->avctx->colorspace),
             .colorlevels = avcol_range_to_mp_csp_levels(ctx->avctx->color_range),
             .chroma_location =