STR (Streaming Data): Difference between revisions

Revision as of 02:22, 23 October 2026 RemmyLee (Hardware and system software pages from the Sony manuals)	Revision as of 02:27, 23 October 2026 RemmyLee (File format pages from the Sony File Formats manual)
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	+	---
	+	title: STR (Streaming Data)
	+	type: format
	+	summary: CD-ROM data format for streaming movies and other time-series data.
	+	category: File formats
	+	info: Extension = .STR
	+	info: Sector size = 2048 bytes (2336 bytes with audio)
	+	---
	+
	+	## Overview
	+
	+	Streaming is the reading and processing of successive data from a CD-ROM. STR is the CD-ROM data format defined for streaming on the PlayStation.[^ff13]
	+
	+	Streaming is used for animation and audio. It also serves other time-series data that changes continuously.[^ff13]
	+
	+	The streaming library is used separately from the other CD-ROM functions.[^ff13]
	+
	+	The bitstream for movie playback comes through streaming. The bitstream does not hold the image size, so the STR header holds the data needed for playback.[^ff13]
	+
	+	## Streaming Data
	+
	+	Streaming data in an STR file is a continuous array of frame data elements.[^ff13]
	+
	+	The contents of a frame depend on the data. In an animation, one frame can hold one still image of the sequence.[^ff13]
	+
	+	The STR format does not set the data type of a frame.[^ff13]
	+
	+	Each frame has its own length and type. One STR file can mix frames of several types and sizes.[^ff13]
	+
	+	## Frame Data
	+
	+	Frame data is divided into 2048-byte sectors. These match the CD-ROM data sectors.[^ff13]
	+
	+	Each sector starts with a 32-byte header. 2016 bytes of data follow.[^ff13]
	+
	+	Each frame begins on a sector boundary. The last sector of a frame is padded with dummy data to the 2048-byte boundary.[^ff13][^ff14]
	+
	+	## Sector Header
	+
	+	The sector header is divided into the following fields:[^ff14][^ff15]
	+
	+	Table: STR sector header
	+
	+	\| Field \| Size \| Contents \|
	+	\| --- \| --- \| --- \|
	+	\| StSTATUS \| 2 bytes \| STR format identifier and version \|
	+	\| StTYPE \| 2 bytes \| Data type of the frame \|
	+	\| StSECTOR_OFFSET \| 2 bytes \| Sector number in the frame \|
	+	\| StSECTOR_SIZE \| 2 bytes \| Number of sectors in the frame \|
	+	\| StFRAME_NO \| 4 bytes \| Frame number of the streaming data, starting from 1 \|
	+	\| StFRAME_SIZE \| 4 bytes \| Frame size in long words \|
	+	\| StUSER \| 16 bytes \| User-defined area \|
	+
	+	All fields are little endian.[^ff15]
	+
	+	An StTYPE with the MSB set is a system-defined format. With the MSB clear it is a user-defined format, and the other 15 bits are free.[^ff14]
	+
	+	The streaming library uses StSECTOR_OFFSET, StSECTOR_SIZE and StFRAME_NO to read frame data in order without missing sectors.[^ff14]
	+
	+	## User-defined Frame Data
	+
	+	User-defined data streams with the MSB of StTYPE set to 0.[^ff15]
	+
	+	A run of streaming data with the same attributes throughout can use one header frame for the whole run. This reduces the total amount of data.[^ff15]
	+
	+	The manual gives an example of streaming data with a header frame.[^ff15]
	+
	+	The example is as follows:
	+
	+
	+	Table: Streaming data with header frame
	+
	+	\| Frame \| StTYPE \|
	+	\| --- \| --- \|
	+	\| Header \| 0x0003 \|
	+	\| Frame0 \| 0x0002 \|
	+	\| Frame1 \| 0x0002 \|
	+	\| Frame3 \| 0x0002 \|
	+
	+	In this example the LSB of StTYPE marks the header frame.[^ff15]
	+
	+	The application can read StTYPE in each frame. The meaning of the frame data can then change with the type of frame.[^ff15]
	+
	+	A header frame can hold CLUT data that is not saved in each frame. It can also hold a table of jumps to frames.[^ff15]
	+
	+	## MDEC Animation
	+
	+	MDEC animation is a system-defined format with StTYPE 0x8001.[^ff16]
	+
	+	Its sector header has the following fields:
	+
	+
	+	Table: MDEC animation sector header
	+
	+	\| Field \| Size \| Contents \|
	+	\| --- \| --- \| --- \|
	+	\| StSTATUS \| 2 bytes \| Status \|
	+	\| StTYPE \| 2 bytes \| Data type, with a channel number for multi-channel streaming \|
	+	\| StSECTOR_OFFSET \| 2 bytes \| Sector number in the frame \|
	+	\| StSECTOR_SIZE \| 2 bytes \| Number of sectors in the frame \|
	+	\| StFRAME_NO \| 4 bytes \| Frame number of the streaming data, starting from 1 \|
	+	\| StFRAME_SIZE \| 4 bytes \| Frame size in long words \|
	+	\| StMOVIE_WIDTH \| 2 bytes \| Width \|
	+	\| StMOVIE_HEIGHT \| 2 bytes \| Height \|
	+	\| StMOVIE_HEADM \| 4 bytes \| Reserved for system \|
	+	\| StMOVIE_HEADV \| 4 bytes \| Reserved for system \|
	+
	+	The channel number is 0 for ordinary streaming.[^ff16]
	+
	+	The frame data of an MDEC animation is [BS](/formats/bs/) data.
	+
	+	## Streaming Data with Audio
	+
	+	The PlayStation plays back ADPCM audio data as specified in the CD-ROM XA standard. Sony calls this XA-ADPCM audio.[^ff16]
	+
	+	XA-ADPCM audio goes from the CD-ROM decoder to the SPU without using main memory. Streaming reads data into main memory, so it cannot play XA-ADPCM audio.[^ff16]
	+
	+	Audio sectors are interleaved with data sectors on the disc. Streaming data with audio places the streaming data in the gaps between the audio sectors.[^ff16][^ff17]
	+
	+	The manual's example uses streaming data at 30 fps (5 sectors per frame). The audio is 37.8 kHz stereo at double speed.[^ff17]
	+
	+	### Sector Size
	+
	+	A sector of ordinary streaming data is 2048 bytes. A sector of streaming data with audio is 2336 bytes.[^ff18]
	+
	+	A data sector has the following parts:
	+
	+
	+	Table: Data sector in streaming data with audio
	+
	+	\| Part \| Size \|
	+	\| --- \| --- \|
	+	\| Subheader \| 8 bytes \|
	+	\| Sector header \| 32 bytes \|
	+	\| Data \| 2016 bytes \|
	+	\| Dummy data \| 280 bytes \|
	+
	+	The audio sectors have the following parts:[^ff18]
	+
	+	Table: XA-ADPCM audio sector for streaming data with audio
	+
	+	\| Part \| Size \|
	+	\| --- \| --- \|
	+	\| Subheader \| 8 bytes \|
	+	\| XA-ADPCM audio \| 2324 bytes \|
	+	\| Dummy data \| 4 bytes \|
	+
	+	The CD-ROM XA standard sets the size of the subheader. The subheader holds flags that tell data sectors from audio sectors.[^ff18]
	+
	+	The dummy data makes an audio sector the same size as a data sector.[^ff18]
	+
	+	The sector header and data areas are the same as in ordinary streaming data.[^ff18]
	+
	+	## References
	+
	+	[^ff13]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-3, Figure 1.
	+	[^ff14]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-4, Figures 2 and 3.
	+	[^ff15]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-5, Figure 4.
	+	[^ff16]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-6, Figure 5.
	+	[^ff17]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-7, Figure 7.
	+	[^ff18]: Sony Computer Entertainment Inc. File Formats. November 1998. Page 1-8, Figures 8 and 9.

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