third attempt at travis config

* upgrade minimum required Rust from 1.17 to 1.20; reffers 0.4.2
  apparently uses std::mem::ManuallyDrop, introduced in 1.20

* install ffmpeg from source (requiring sudo access) rather than using
  the ancient one from Ubuntu Trusty to meet the minimum version
  requirements specified in ffmpeg/build.rs.

.travis.yml

@@ -1,25 +1,26 @@
+dist: trusty
+sudo: required
 language: rust
 rust:
   - stable
   - nightly
-  - 1.17.0
+  - 1.20.0
 addons:
   apt:
     packages:
       - build-essential
-      - libavcodec-dev
-      - libavformat-dev
-      - libavutil-dev
       - libncurses5-dev
       - libncursesw5-dev
       - libsqlite3-dev
       - libssl-dev
       - pkg-config
+      - yasm
 matrix:
   allow_failures:
     - rust: nightly
 cache: cargo
 script:
+  - (git clone --depth 1 -b "release/3.4" https://github.com/FFmpeg/FFmpeg.git && cd FFmpeg && ./configure --enable-shared && make && sudo make install && sudo ldconfig)
   - cargo build --verbose --all
   - cargo test --verbose --all
   - 'if [ $TRAVIS_RUST_VERSION = nightly ]; then cargo bench --verbose --all; fi'

guide/install-manual.md

@@ -49,8 +49,8 @@ all non-Rust dependencies:
                    libssl-dev \
                    pkgconf
 
-Next, you need Rust 1.17+ and Cargo. The easiest way to install them is by following
-the instructions at [rustup.rs](https://www.rustup.rs/).
+Next, you need Rust 1.20+ and Cargo. The easiest way to install them is by
+following the instructions at [rustup.rs](https://www.rustup.rs/).
 
 Finally, building the UI requires [yarn](https://yarnpkg.com/en/).
 

scripts/script-functions.sh

@@ -40,7 +40,7 @@ fi
 NODE_MIN_VERSION="8"
 YARN_MIN_VERSION="1.0"
 CARGO_MIN_VERSION="0.2"
-RUSTC_MIN_VERSION="1.17"
+RUSTC_MIN_VERSION="1.20"
 FFMPEG_MIN_VERSION="55.1.101"
 FFMPEG_RELEASE_VERSION="3.4"