helix mobile producer on-demand user's guide - RealPlayer

Helix Mobile Producer On-Demand User’s GuideBe aware that the addition of data such as hint tracks and headers to audio orvideo streams during the encoding process results in the encoded files beingsomewhat larger than the sum of the encoded media bit rates multiplied bythe duration of the file ((audio bit rate + video bit rate) x duration). This doesnot affect the bit rate or quality of the media, because this additional dataremains on the server and does not get streamed to the client.Note: The hint track is required by the streaming server tooptimize the streaming experience. A 3GPP media file musthave a hint track in order to be properly streamed from moststreaming servers. The hint track is not required if the mediafile is to be downloaded and played locally and not streamedfrom a server. To avoid having Helix Mobile Producer On-Demand add a hint track to such a file, select the Basic-profilecheck box on the Export tab before encoding the audio or videoclip.Progressive-download profile (MPEG-4 and H.263 encoders only)By default, MPEG-4 files are generated with the metadata following the rawmedia data, which results in efficient writing of the MPEG-4 files. However,this means that a player must completely download an MPEG-4 file beforeplaying it, as the player cannot begin playback until it has received themetadata.If you have selected the Progressive-download profile option, the MPEG-4 fileis reordered at the end of the encoding process so that the metadata appearsat the beginning of the file. This enables a player to download and play thecontent at the same time, rather than having to wait for the entire file to bedownloaded before playing it.Maximum Packet Size (3GPP, MPEG-4 and RealMedia export types only)The maximum packet size should be less than the maximum transmissionunit (MTU) of the network over which the content will be streamed. Packetheader "overhead" should also be taken into account in this calculation. Bydefault, the maximum packet size is configured to be appropriate for generalInternet usage, for which the MTU of 1,500 bytes takes into account UDP andIP packet headers. For other types of target networks, such as ATM or wirelessnetworks, the maximum packet size should be adjusted to reflect thecorresponding larger or smaller MTU.48