Finally got video with audio working on my Due.
Used SSD1351 OLED @128*128 RGB565 via SPI DMA, AD7302 8 bit parallel DAC and SD card.
Can see the demo video at Arduino Due - Video and Sound! - YouTube
Video description has a lot of information.
(currently hoping it meets fair use policy as the video in the demo was "good enough" to be pinged by the youtube copyright robot).
Built the video converter from scratch using FFMPEG to read the video and audio frames.