Editing Portable media player (section)

==Common audio formats==
There are three categories of audio formats:

* Uncompressed [[PCM]] audio: Most players can also play uncompressed [[PCM]] in a container such as [[WAV]] or [[Audio Interchange File Format|AIFF]].
* [[Lossless audio]] formats: These formats maintain the [[Hi-fi]] quality of every song or disc. These are the ones used by CDs, many people recommend the use of lossless audio formats to preserve the CD quality in audio files on a desktop. Lossless formats include [[Apple Lossless]] and [[FLAC]].
* [[Lossy compression]] formats: Most audio formats use [[lossy compression]], to produce as small as possible a file compatible with the desired sound quality. There is a [[trade-off]] between size and sound quality of lossily compressed files; most formats allow different combinations—e.g., MP3 files may use between 32 (worst), 128 (reasonable) and 320 (best) kilobits per second.<ref>{{cite web|url=http://nigelcoldwell.co.uk/audio/|title=Comparison of audio compression using ogg vorbis, mp3 CBR & VBR, flac and wma at different bit rates|publisher=nigelcoldwell.co.uk|url-status=live|archive-url=https://web.archive.org/web/20110727193035/http://nigelcoldwell.co.uk/audio/|archive-date=27 July 2011|df=dmy-all}}</ref>

There are also royalty-free lossy formats like [[Vorbis]] for general music and [[Speex]] and [[Opus (audio format)|Opus]] used for voice recordings. When "ripping" music from CDs, many people recommend the use of [[lossless audio]] formats to preserve the CD quality in audio files on a desktop, and to transcode the music to [[lossy compression]] formats when they are copied to a portable player.<ref name="guardian">{{cite web|url=https://www.theguardian.com/technology/2014/jul/13/music-lossless-rip-cds-tech-questions-answered|title=How best to rip 1,500 music CDs? Your tech questions answered|work=The Guardian Technology|date=13 July 2014|url-status=live|archive-url=https://web.archive.org/web/20161015193527/https://www.theguardian.com/technology/2014/jul/13/music-lossless-rip-cds-tech-questions-answered|archive-date=15 October 2016|df=dmy-all}}</ref> The formats supported by a particular audio player depends upon its [[firmware]]; sometimes a firmware update adds more formats. MP3 and [[Advanced Audio Coding|AAC]] are dominant formats,<ref name="guardian" /> and are almost universally supported.<ref>{{cite web|url=http://gale.cengage.com/reference/peter/200712/amazon.htm|title=Péter's Digital Reference Shelf – Amazon MP3|access-date=17 April 2008|url-status=live|archive-url=https://web.archive.org/web/20080505011750/http://gale.cengage.com/reference/peter/200712/amazon.htm|archive-date=5 May 2008|df=dmy-all}}</ref>

=== Video and chipsets ===
Chipsets and file formats that are particular to some PMPs:
*Anyka is a chip that's used by many MP4 Players. It supports the same formats as Rockchip.
*[[Fuzhou]] [[Rockchip]] Electronics's [[video processing]] ''[[Rockchip]]'' has been incorporated into many MP4 players, supporting [[Audio Video Interleave|AVI]] with no [[B frames]] in [[MPEG-4 Part 2]] (not [[MPEG-4 Part 14|Part 14]]), while [[MPEG-1 Audio Layer II|MP2]] audio compression is used.<ref>{{cite web |title=Leading Chinese MP4 IC Design Houses' R&D and Product Strategies Research Report # MIC1324 |url=http://www.electronics.ca/reports/multimedia/mic_mp4chips_design.html |url-status=dead |archive-url=https://web.archive.org/web/20080311000040/http://www.electronics.ca/reports/multimedia/mic_mp4chips_design.html |archive-date=2008-03-11 |publisher=Electronics.ca Publications}}</ref> The clip must be padded out, if necessary, to fit the resolution of the display. Any slight deviation from the supported format results in a ''Format Not Supported'' error message.
*Some players, like the Onda VX979+, have started to use chipsets from [[Ingenic]], which are capable of supporting [[RealNetworks]]'s video formats.<ref>{{cite web |date=2007-11-28 |title=Teclast announces the M series |url=http://www.haomp.com/page/2/ |url-status=dead |archive-url=https://web.archive.org/web/20080323153358/http://www.haomp.com/page/2/ |archive-date=23 March 2008 |access-date=2008-03-18 |publisher=haomp |df=dmy-all}}</ref> Also, players with [[SigmaTel]]-based technology are compatible with SMV (SigmaTel Video).

==== AMV ====
{{main|AMV video format}}

The image compression algorithm of this format<ref>{{cite web |last=Israelsen |first=Paul D. |date=1993-09-21 |title=United States Patent 5247357 |url=http://www.freepatentsonline.com/5247357.html |access-date=2007-12-07}}</ref> is inefficient by modern standards (about 4 pixels per byte, compared with over 10 pixels per byte for [[MPEG-2#DVD-Video|MPEG-2]]). There are a fixed range of resolutions (96 × 96 to 208 × 176 pixels) and framerates (12 or 16 [[Frames per second|frames]]) available. However it can be used with limited hardware requirements. A 30-minute video would have a filesize of approximately 100 MB at a 160 × 120 resolution.<ref name="codecdoc">{{cite web |author=voroshil |date=2007-10-15 |title=AmvDocumentation |url=http://code.google.com/p/amv-codec-tools/wiki/AmvDocumentation |access-date=2008-04-06 |publisher=Google Code}}</ref>

==== MTV ====
The MTV video format (no relation to the [[MTV|cable network]]) consists of a 512-byte file header that operates by displaying a series of raw image frames during [[MP3]] playback.<ref name="codecdoc" /> During this process, audio frames are passed to the chipset's decoder, while the memory pointer of the display's hardware is adjusted to the next image within the video stream. This method does not require additional hardware for decoding, though it will lead to a higher amount of memory consumption. For that reason, the storage capacity of an MP4 player that uses MTV files is effectively less than that of a player that decompresses files on the fly.