TimTaiLieu.vn - Tài liệu, ebook, giáo trình, đồ án, luận văn

Audio Compression (MPEG and Others) As with video a number of compression techniques have been applied to audio. RECAP (Already Studied) Traditional lossless compression methods (Huffman, LZW, etc.) usually don’t work well on audio compression For the same reason as in image and video compression: Too much change variation in data over a sho...

70 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 860 | Lượt tải: 0

MPEG-4 Main aim: interactivity. Previous MPEG-1/2 were frame based. Virtually no interactivity. MPEG-4 is not only aimed to improve compression, but to improve functionality and interactivity. MPEG-4 targets: Digital TV. Interactive graphics, computer games. Interactive multimedia, WWW. MPEG-4 addresses the needs of authors, service provid...

33 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 879 | Lượt tải: 0

We need to compress video (more so than audio/images) in practice since: 1 Uncompressed video (and audio) data are huge. In HDTV, the bit rate easily exceeds 1 Gbps | big problems for storage and network communications. E.g. HDTV: 1920 x 1080 at 30 frames per second, 8 bits per YCbCr (PAL) channel = 1.5 Gbps. 2 Lossy methods have to be employ...

63 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 1164 | Lượt tải: 0

What is JPEG? JPEG: Joint Photographic Expert Group | an international standard since 1992. Works with colour and greyscale images. Up to 24 bit colour images (unlike GIF) Target photographic quality images (unlike GIF) Suitable for many applications e.g. satellite, medical, general photography. . .

25 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 1002 | Lượt tải: 0

Moving into the Frequency Domain Frequency domains can be obtained through the transformation from one (time or spatial) domain to the other (frequency) via Fourier Transform (FT) (see Chapter 2 and recall from CM2202) | MPEG Audio . Discrete Cosine Transform (DCT) (new) | Heart of JPEG and MPEG Video, MPEG Audio. Note: We mention some image...

33 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 799 | Lượt tải: 0

Modeling and Compression We are interested in modeling multimedia data. To model means to replace something complex with a simpler (= shorter) analog. Some models help understand the original phenomenon/data better:

78 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 766 | Lượt tải: 0

Digital Audio Effects Having learned to make basic sounds from basic waveforms and more advanced synthesis methods lets see how we can at some digital audio effects. These may be applied: As part of the audio creation/synthesis stage | to be subsequently filtered, (re)synthesised At the end of the audio chain | as part of the production/mas...

118 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 740 | Lượt tải: 0

What is MIDI? No Longer Exclusively the Domain of Musicians. MIDI provides a very low bandwidth alternative on the Web: transmit musical and certain sound effects data also now used as a compression control language (modified) See MPEG-4 Section soon See also HTML5 soon

51 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 777 | Lượt tải: 0

Some Practical Multimedia Digital Audio Applications: Having considered the background theory to digital audio processing, let’s consider some practical multimedia related examples: Digital Audio Synthesis | making some sounds Digital Audio Effects | changing sounds via some standard effects. MIDI | synthesis and effect control and compressi...

98 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 828 | Lượt tải: 0

Microphone: Receives sound Converts to analog signal. Computer like discrete entities Need to convert Analog-to-Digital | Dedicated Hardware (e.g. Soundcard)

24 trang | Chia sẻ: nguyenlinh90 | Ngày: 17/07/2019 | Lượt xem: 768 | Lượt tải: 0