allows one to fit given media into smaller storage space (for instance, fitting a DVD onto a Video CD), or over a lower bandwidth channel. Image scaling Changing the picture size of video is known as transsizing, and is used if the output resolution differs from the resolution of the media. On a powerful enough device, image scaling can be done on playback, but it can also be done by re-encoding, particularly as part of transrating (such as a downsampled image requiring a lower bitrate). One can also use formats with bitrate peeling, that allow one to easily lower the bitrate without re-encoding, but quality is often lower than a re-encode. For example, in Vorbis bitrate peeling as of 2008, the quality is inferior to re-encoding. Drawbacks The key drawback of transcoding in lossy formats is decreased quality. Compression artifacts are cumulative, so transcoding causes a progressive loss of quality with each successive generation, known as digital generation loss. For this reason, transcoding (in lossy formats) is generally discouraged unless unavoidable. For users wanting to be able to re-encode audio into any format, and for digital audio editing, it is best to retain a master copy in a lossless format (such as FLAC, ALAC, TTA, WavPack, and others) that take around half the storage space needed when compared to original uncompressed PCM formats (such as WAV, and AIFF), as lossless formats usually have the added benefit of having meta data options, which are either completely missing or very limited in PCM formats. These lossless formats can be transcoded to PCM formats or transcoded directly from one lossless format to another lossless format, without any loss in quality. They can be transcoded into a lossy format, but these copies will then not be able to be transcoded into another format of any kind (PCM, lossless, or lossy) without a subsequent loss of quality. For image editing users are advised to capture or save images in a raw or uncompressed format, and then edit a copy of that master version, only converting to lossy formats if smaller file sized images are needed for final distribution. As with audio, transcoding from lossy format to another format of any type will result in a loss of quality. For video editing, (for video converting), images are normally compressed directly during the recording process due to the huge file sizes that would be created if they