Lecture 8 video_sound
- 1. Application Engineering and Development Topic: Video and Sound Topic Number: 8
- 2. Key topics / learning outcomes of this lecture • Learn about video, compression and file size • Learn about digital audio, sample rate and open source software for recording 2
- 3. Video for Android • What is a video? – a series of images that display in sequence to create movement in time with the real world; – images are called ‘frames’ in video; • How many images make a video? – a motion picture film will typically have 24 frames display every one second; – early silent films had frame rates between 26 – 24 frames per second; • cameras were manually managed by turning a wheel holding the film, so the camera manager could slow the frame rate down, to match the film mood!
- 4. Importance of frame rate • 48 fps is currently being trialled in the film industry: – this will reduce flicker; – this will reduce motion blur • motion blur occurs when images being filmed move faster in the real world than the frame rate being captured; • 300 fps has been tested by BBC research for use in sports broadcasts: – 300 fps can be converted to both 50 and 60 fps transmission formats without major issues B4004A L1 4
- 5. Image size / resolution B4004A L1 5
- 6. In photoshop, inspect the element Image size: 850.8K Width 710 px Height 409 px B4004A L1 6
- 7. Image compression • This image was possibly originally around 3MB when it was first taken; • It has been compressed to achieve an image size of 850.8KB: – this is still quite a high KB size, it could be reduced a lot further, making transmission faster as there are less bits; – the image could be compressed further, by running further jpeg (or other) compression algorithms on the content to reduce the size; – the image can be made physically smaller, this will reduce the file size also; B4004A L1 7
- 8. Video Compression Year Standard Publisher Popular Implementations 1984 H.120 ITU-T 1988 H.261 ITU-T Videoconferencing, Videotelephony 1993 MPEG-1 Part 2 ISO, IEC Video-CD 1995 H.262/MPEG-2 Part 2 ISO, IEC, ITU-T DVD Video, Blu-ray, Digital Video Broadcasting, SVCD 1996 H.263 ITU-T Videoconferencing, Videotelephony, Video on Mobile Phones (3GP) 1999 MPEG-4 Part 2 ISO, IEC Video on Internet (DivX, Xvid ...) 2003 H.264/MPEG-4 AVC Sony, Panasonic, Sam sung,ISO, IEC, ITU-T Blu-ray, HD DVD Digital Video Broadcasting,iPod Video, Apple TV, 2009 VC-2 (Dirac) SMPTE Video on Internet, HDTV broadcast, UHDTV 2013 H.265 ISO, IEC, ITU-T B4004A L1 8
- 9. YouTube use H.264 codec B4004A L1 9
- 10. Video - Flash Player • There is no longer support for Flash Player as it is very processor consumptive and drains battery. • Avoid designing with Flash until the issues are resolved. B4004A L1 10
- 11. Tips to reduce video file size • Keep the video short in terms of time; • Keep the video camera completely still where possible, when actually filming content – compression will be more efficient if the background of the subject remains still; • Reduce the physical size of the video before filming, whilst keeping the aspect ratio • Run the video through a good quality and appropriate compression technique. B4004A L1 11
- 12. Embed Video within Android App • Put the final video into the app resources, the res/raw folder. • use Java to code or • use the YouTube Player API for Android B4004A L1 12
- 13. … end of Video section… … next is Audio … B4004A L1 13
- 14. What is Audio Audio used to be created by recording sound waves; B4004A L1 14 Digital audio takes those sound waves and reproduces them digitally.
- 15. Sampling (signal processing) • A sound wave is a continuous signal • A sample refers to a set of values at a given point • this is one cycle; • this = 1hz; • this equals 1 hz per second; B4004A L1 15
- 16. Sound Hz (Hertz) • The more hertz, the different the sound, known also as the pitch; Voice Frequency Male 85 – 180 Hz Female 165 – 255 Hz B4004A L1 16
- 17. Sample rate • Sample rate for a CD is 44,100 samples from the sound wave per second; B4004A L1 17
- 18. Decibels (Loudness) Noise Decibels Whisper in quiet library at 6 feet 30dB Normal conversation at 3 feet 60dB Normal piano practice 70dB Loud rock concert 115dB Jet engine at 100 feet 140dB Death of hearing tissue 180dB Loudest sound possible 194dB B4004A L1 18
- 19. Creating and recording sound Copyright issues • when using existing sounds, ensure there are no copyright issues’ • generally, any music that was published 75 years ago becomes copyright free; • a small sound loop of less than 3 seconds is allowed to be made from published sound which is not yet copyright free; B4004A L1 19
- 20. Audacity • well known open source software for sound manipulation: B4004A L1 20
- 21. Audacity setup • Facility to – connect a microphone (if required); – set up an audio host and playback device; – select input; – make a test recording; – edit the recording; – save the recording in the appropriate file format; B4004A L1 21
- 22. Using Audio with Android Starting an Activity - request audio focus B4004A L1 22
- 23. Essential work for next week • Please consult the OLE for details of: – Essential readings* – Seminar/workshop preparation work* – Recommended further readings – Any additional learning * Essential readings and preparation work must always be completed in time for the next session 23
- 24. End of presentation © Pearson College 2013