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--- tanszek:oktatas:techcomm:mpeg_compression [2024/11/19 11:01] – [Additional Information on MPEG Compression] knehez
+++ tanszek:oktatas:techcomm:mpeg_compression [2024/11/19 11:06] (current) – [MPEG] knehez
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 ===== Principles of MPEG Compression =====
-The human ear perceives sound in the frequency range of 20 Hz to 20 kHz, with the most sensitive range being between 2-4 kHz (note: a tuning fork vibrates at a frequency of 440 Hz). A key characteristic of human hearing is that when two sounds of similar frequencies are played simultaneously, the one with higher intensity masks the one with lower intensity. This masking effect also occurs if the lower-intensity sound starts 2 ms earlier and ends approximately 15 ms later than the higher-intensity sound of a nearby frequency.
+**MPEG** compression offers various methods for both video and audio. In **MPEG**, it is crucial to keep audio and video synchronized over time, so audio and video data include timestamps.
-Quantization should be performed with particular attention to the fact that frequencies between 2-4 kHz require higher precision than those in the 10-20 kHz range.
-MPEG compression offers various methods for both video and audio. In video compression, MPEG takes into account changes between individual frames. It defines keyframes (I-frames) that compress the entire frame using the previously known JPEG method, while intermediate frames (P-frames, B-frames) contain information about changes. This is particularly important during fast-forward operations, as a full frame for a P-frame can only be reconstructed starting from the preceding I-frame since P-frames do not contain the complete image, only the changes.
-In MPEG, it is crucial to keep audio and video synchronized over time, so both audio and video include timestamps.
-==== Additional Information on MPEG Compression ====
 **MPEG** (Moving Picture Experts Group) compression is a widely used standard for reducing the file size of video and audio content while maintaining an acceptable level of quality. It achieves high compression ratios by eliminating redundant information spatially within a frame and temporally between consecutive frames.
-Temporal Redundancy Removal: Temporal redundancy exists because consecutive video frames often have many similarities. MPEG compression uses motion compensation to identify and encode only the differences between frames, instead of storing every frame in full detail. This is done by using the following frame types:
+**Temporal Redundancy Removal**: Temporal redundancy exists because consecutive video frames often have many similarities. MPEG compression uses motion compensation to identify and encode only the differences between frames, instead of storing every frame in full detail. This is done by using the following frame types:
   * **I-frames** (Intra-coded frames): are complete images, compressed independently of other frames, much like a JPEG image.
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 ==== Container Types for MPEG Compression ====
-MPEG compression is often used in conjunction with different container formats that store video, audio, subtitles, and other metadata. Some common container formats include:
+**MPEG** compression is often used with different container formats that store video, audio, subtitles, and other metadata. Some common container formats include:
-**MP4 (MPEG-4)**: MP4 is one of the most popular container formats used to store video, audio, subtitles, and images. It is highly compatible with various devices and platforms, making it ideal for streaming and sharing. MP4 supports various codecs, including MPEG-4 and H.264, and is commonly used for online video and mobile applications.
+**MP4 (MPEG-4)**: MP4 is one of the most popular container formats for storing video, audio, subtitles, and images. It is highly compatible with various devices and platforms, making it ideal for streaming and sharing. MP4 supports various codecs, including MPEG-4 and H.264, and is commonly used for online video and mobile applications.
-**AVI (Audio Video Interleave)**: AVI is a container format introduced by Microsoft. It is known for its simplicity and compatibility with many media players. However, AVI files tend to be larger compared to other formats due to limited compression options. While it can use various codecs, AVI is less efficient for streaming applications.
+**AVI (Audio Video Interleave)**: AVI is a container format introduced by Microsoft. It is known for its simplicity and compatibility with many media players. However, AVI files tend to be larger than other formats due to limited compression options. While it can use various codecs, AVI is less efficient for streaming applications.
-**FLV (Flash Video)**: FLV is a container format developed by Adobe and commonly used for delivering video content over the internet. It was widely used on platforms like YouTube in the early days. FLV supports streaming and progressive download, making it suitable for web-based video, but it has fallen out of favor in recent years due to the decline of Adobe Flash.
+**FLV (Flash Video)**: FLV is a container format developed by Adobe and commonly used for delivering video content over the internet. It was widely used on platforms like YouTube in the early days. FLV supports streaming and progressive download, making it suitable for web-based video, but it has fallen out of favour in recent years due to the decline of Adobe Flash.
-**MKV (Matroska Video)**: MKV is an open-source container format that can hold unlimited video, audio, subtitle tracks, and other metadata. It is highly versatile and often used for HD video. MKV is known for its support of different codecs and its flexibility, making it a popular choice for storing Blu-ray rips and high-quality video files.
+**MKV (Matroska Video)**: MKV is an open-source container format with unlimited video, audio, subtitle tracks, and other metadata. It is highly versatile and often used for HD video. MKV is known for its support of different codecs and its flexibility, making it a popular choice for storing Blu-ray rips and high-quality video files.
-**MPEG-TS (Transport Stream)**: MPEG-TS is a container format designed for broadcasting and streaming applications. It is used for live video broadcasting, such as digital television and over-the-air broadcasts, as it can handle errors in transmission and provide synchronization for continuous streams.
+**MPEG-TS (Transport Stream)**: MPEG-TS is a container format designed for broadcasting and streaming applications. It is used for live video broadcasting, such as digital television and over-the-air broadcasts, as it can handle transmission errors and provide synchronization for continuous streams.
 **MOV**: Developed by Apple, MOV is similar to MP4 and is often used with Apple's QuickTime framework. It can store multiple tracks, including video, audio, and text, making it suitable for editing and playback. MOV files are commonly used in professional video editing environments.
-Each of these container formats has its own advantages and is chosen based on the specific requirements of the content delivery, such as compatibility, compression efficiency, and intended use. The container format determines how the compressed video and audio streams are packaged together, including information on how the video frames, audio samples, and synchronization data are stored. Video is typically stored as a series of compressed frames (using codecs like H.264 or H.265), while audio is stored as compressed streams (e.g., MP3, AAC). The container also includes metadata that helps synchronize audio and video during playback, ensuring that lip-sync and timing are maintained. This affects playback capabilities and compatibility with different devices and software.
+Each of these container formats has its own advantages and is chosen based on the specific requirements of the content delivery, such as compatibility, compression efficiency, and intended use. The container format determines how the compressed video and audio streams are packaged together, including information on storing the video frames, audio samples, and synchronization data. Video is typically stored as a series of compressed frames (using codecs like H.264 or H.265), while audio is stored as compressed streams (e.g., MP3, AAC). The container also includes metadata that helps synchronize audio and video during playback, ensuring that lip-sync and timing are maintained. This affects playback capabilities and compatibility with different devices and software.