Restore Libav support

Libav has been broken due to the hwdec changes. This was always a
temporary situation (depended on pending patches to be merged), although
it took a bit longer. This also restores the travis config.

One code change is needed in vd_lavc.c, because it checks the AV_PIX_FMT
for videotoolbox (as opposed to the mpv format identifier), which is not
available in Libav. Add an ifdef; the affected code is for a deprecated
option anyway.

.travis.yml

@@ -6,6 +6,7 @@ os:
 env:
   matrix:
     - LIBAV=ffmpeg-git
+    - LIBAV=libav-git
   global:
     # Coverity token
     - secure: "H21mSRlMhk4BKS0xHZvCFGJxteCP0hRVUxTuNfM2Z9HBsyutuLEYMtViLO86VtM+Tqla3xXPzUdS4ozLwI72Ax/5ZUDXACROj73yW6QhFB5D6rLut12+FjqC7M33Qv2hl0xwgNBmR5dsm1ToP37+Wn+ecJQNvN8fkTXF+HVzOEw="

video/decode/vd_lavc.c

@@ -738,8 +738,10 @@ static int init_generic_hwaccel(struct dec_video *vd, enum AVPixelFormat hw_fmt)
 
     AVHWFramesContext *new_fctx = (void *)new_frames_ctx->data;
 
+#if LIBAVCODEC_VERSION_MICRO >= 100
     if (ctx->hwdec.pix_fmt == AV_PIX_FMT_VIDEOTOOLBOX)
         new_fctx->sw_format = imgfmt2pixfmt(vd->opts->videotoolbox_format);
+#endif
     if (vd->opts->hwdec_image_format)
         new_fctx->sw_format = imgfmt2pixfmt(vd->opts->hwdec_image_format);
 

wscript

@@ -421,7 +421,7 @@ ffmpeg_pkg_config_checks = [
 ]
 libav_pkg_config_checks = [
     'libavutil',     '>= 56.6.0',
-    'libavcodec',    '>= 58.5.0',
+    'libavcodec',    '>= 58.8.0',
     'libavformat',   '>= 58.1.0',
     'libswscale',    '>= 5.0.0',
     'libavfilter',   '>= 7.0.0',