Working with STR Video

STR (Stream) files contain MDEC-compressed video with interleaved XA audio, providing full-motion video capabilities for PlayStation games.

What is STR Video?

STR files are mixed-mode video streams that:

Contain MDEC-compressed video frames
Interleave XA audio for synchronized sound
Use alternating Mode 2 Form 1 (video) and Form 2 (audio) sectors
Stream directly from CD during playback
Support various resolutions and frame rates

STR File Structure

STR files contain interleaved sectors:

Mode 2 Form 1 sectors: MDEC video data + error correction
Mode 2 Form 2 sectors: XA ADPCM audio data
Subheaders: Define each sector’s type and parameters

The PlayStation’s hardware demultiplexes the stream, sending video to MDEC decoder and audio to the SPU.

Adding STR Video to Your ISO

Prepare STR Video Files

Ensure your STR files are properly formatted:

Files must be in raw 2336-byte sector format
Must contain valid MDEC video frames
Must have proper sector subheaders
Audio and video must be correctly interleaved

Use PlayStation SDK tools or community converters to create STR files.

mkpsxiso validates sector subheaders and will report errors for improperly ripped or encoded STR files. Always verify your source files.

Add STR Files to XML

Define STR files with type="mixed" in your directory tree:

<directory_tree>
  <dir name="movies">
    <file name="intro.str" type="mixed" source="video/intro.str"/>
    <file name="ending.str" type="mixed" source="video/ending.str"/>
    <file name="cutscene1.str" type="mixed" source="video/scene1.str"/>
  </dir>
</directory_tree>

You can use type="str" as an alias for type="mixed". All three types (mixed, str, xa) are functionally identical and just tell mkpsxiso to handle the file as mixed-mode.

Optimize File Placement

Place STR files strategically for optimal playback:

<directory_tree>
  <!-- System files -->
  <file name="system.cnf" source="system.cnf"/>
  <file name="game.exe" source="game.exe"/>
  
  <!-- Intro movie near start of disc -->
  <file name="intro.str" type="str" source="video/intro.str"/>
  
  <!-- Level data -->
  <dir name="levels">
    <file name="level1.dat" source="levels/level1.dat"/>
    
    <!-- Cutscene after level data -->
    <file name="scene1.str" type="str" source="video/level1_scene.str"/>
    
    <file name="level2.dat" source="levels/level2.dat"/>
    <file name="scene2.str" type="str" source="video/level2_scene.str"/>
  </dir>
</directory_tree>

Place STR files immediately after the game content that triggers them. This minimizes seek time when transitioning from gameplay to cutscene.

Build and Test

Build your ISO and verify video playback:

mkpsxiso myproject.xml

Test to ensure:

Video plays smoothly without stuttering
Audio stays synchronized with video
No visual artifacts or corruption
Proper frame rate maintenance

STR Sector Details

Mixed Mode Encoding

mkpsxiso automatically handles mixed-mode encoding:

Reads each sector’s subheader
Detects Form 1 (video) vs Form 2 (audio)
Applies appropriate encoding:
- Form 1: Adds error detection (EDC) and error correction (ECC)
- Form 2: Adds only EDC, no ECC

Subheader Information

Each sector’s subheader contains:

File Number: Stream identifier
Channel Number: For multi-stream files
Submode Byte: Form 1 or Form 2 flag
Coding Info: Audio parameters (for audio sectors)

Data Sector Detection

mkpsxiso uses improved logic to identify:

Mode 2 Form 1 sectors (video data)
Mode 2 Form 2 sectors (audio data)
Proper interleaving patterns

This prevents STR/XA files from being incorrectly extracted as DATA format.

Creating STR Files

From Video Sources

Convert standard video formats to STR:

# Example using jPSXdec (community tool)
jpsxdec -f video.str -it movie.avi

From PlayStation SDK

Use official SDK tools:

# Example conversion (requires PsyQ SDK)
movconv input.avi output.str

Extracting from Games

Extract STR files from existing games:

dumpsxiso -x game.bin

Extracted STR files can serve as:

Format references
Templates for your own videos
Test cases for playback code

Common STR Patterns

Opening Cinematic

<!-- Place intro video early for quick access -->
<directory_tree>
  <file name="system.cnf" source="system.cnf"/>
  <file name="game.exe" source="game.exe"/>
  <file name="intro.str" type="str" source="movies/opening.str"/>
  <!-- Rest of game data -->
</directory_tree>

Level Transitions

<dir name="levels">
  <!-- Level 1 -->
  <file name="level1.dat" source="levels/1.dat"/>
  <file name="l1_end.str" type="str" source="movies/level1_complete.str"/>
  
  <!-- Level 2 -->
  <file name="level2.dat" source="levels/2.dat"/>
  <file name="l2_end.str" type="str" source="movies/level2_complete.str"/>
</dir>

Multiple Endings

<dir name="endings">
  <file name="good.str" type="str" source="movies/good_ending.str"/>
  <file name="bad.str" type="str" source="movies/bad_ending.str"/>
  <file name="true.str" type="str" source="movies/true_ending.str"/>
</dir>

Audio in STR Files

Synchronized Audio

STR audio is interleaved with video:

Sector 1: Video frame 1
Sector 2: Audio chunk 1
Sector 3: Video frame 2
Sector 4: Audio chunk 2
...

This ensures audio-video synchronization during streaming.

Audio Parameters

XA audio in STR files typically uses:

Sample Rate: 37800 Hz
Channels: Stereo
Compression: ADPCM Level C
Bits: 4-bit ADPCM

Silent Video

STR files can contain video-only (no audio):

Only Mode 2 Form 1 sectors
No audio sectors interleaved
Simpler structure, slightly higher video data rate

Video Parameters

Resolution

Common PlayStation STR resolutions:

320x240: Standard quality, lower data rate
320x224: NTSC-friendly resolution
384x240: Higher quality, more data
640x240: High quality, requires careful optimization

Frame Rate

Typical frame rates:

15 fps: Standard for PlayStation FMV
20 fps: Smoother motion
30 fps: High quality, requires more disc space

15 fps is the most common frame rate for PlayStation STR videos. It provides acceptable quality while keeping file sizes manageable for CD streaming.

Color Depth

MDEC video uses:

15-bit color (5-5-5 RGB)
24-bit color (8-8-8 RGB) with quantization

Higher color depth increases file size proportionally.

EDC and ECC Handling

Form 1 Sectors (Video)

Video sectors receive full error protection:

EDC: Error Detection Code
ECC: Error Correction Code

This ensures video data integrity during playback.

Form 2 Sectors (Audio)

Audio sectors receive only EDC:

<track type="data" xa_edc="true">
  <!-- Form 2 sectors include EDC -->
</track>

Or without EDC:

<track type="data" xa_edc="false">
  <!-- Form 2 sectors without EDC -->
</track>

The xa_edc attribute controls EDC generation for all Form 2 sectors, including those in STR files.

Troubleshooting

Video Playback Issues

If video doesn’t play correctly:

Verify sector format: Ensure file is in 2336-byte sector format
Check subheaders: Validate Form 1/Form 2 flags are correct
Test source file: Try playing in jPSXdec or other STR player
Examine interleaving: Confirm audio/video sectors alternate properly

Audio Desynchronization

If audio drifts out of sync:

Check frame rate matches expected value
Verify audio sample rate is correct
Ensure no sectors are missing or corrupted
Test on actual hardware (emulators may behave differently)

Stuttering or Dropped Frames

If playback stutters:

Optimize file placement: Move STR closer to related content
Reduce data rate: Use lower resolution or frame rate
Check disc layout: Ensure no excessive seeking required
Test on hardware: CD drive speed affects streaming performance

Incorrect Sector Detection

If mkpsxiso reports sector errors:

Files may have been incorrectly extracted
Sector headers might be malformed
File might not be genuine STR format

mkpsxiso performs strict validation of STR sector formats. Files must have valid Mode 2 Form 1/Form 2 sector structures.

Performance Optimization

Bitrate Considerations

PlayStation CD streaming limits:

Maximum: ~300 KB/s (2x speed)
Safe rate: ~150 KB/s (1x speed)
Conservative: ~100 KB/s (with seek overhead)

Keep total data rate below these limits for reliable playback.

File Size Management

Resolution  Frame Rate  Duration  Approximate Size
320x240     15 fps      60s       15-20 MB
320x240     15 fps      120s      30-40 MB
384x240     15 fps      60s       20-25 MB
320x240     30 fps      60s       30-40 MB

Balance quality and disc space based on your game’s needs.

Strategic Placement

Optimal STR Placement:

Intro video near disc start (LBA 24-100)
In-game cutscenes after related level data
Ending sequences at disc end
Group multiple cutscenes if played sequentially

Best Practices

Quality Guidelines

Use 320x240 at 15 fps for standard cutscenes
Reserve higher quality for important cinematics
Test on real hardware to verify streaming performance
Include audio sync markers for long videos

File Organization

<!-- Good organization -->
<dir name="fmv">
  <file name="intro.str" type="str" source="fmv/intro.str"/>
  <file name="scene01.str" type="str" source="fmv/scene01.str"/>
  <file name="scene02.str" type="str" source="fmv/scene02.str"/>
  <file name="ending.str" type="str" source="fmv/ending.str"/>
</dir>

Compression Balance

Find the right balance:

Too much compression: Visual artifacts, blocky video
Too little compression: Files too large, streaming issues
Optimal: Just enough compression to maintain quality at target bitrate

Next Steps

Combine STR video with XA Audio for rich multimedia
Add CDDA Audio tracks for opening themes
Optimize all media with LBA placement
Learn about Building ISOs for complete projects

Getting Started

Commands

XML Configuration

Guides

Reference

​What is STR Video?

​STR File Structure

​Adding STR Video to Your ISO

​STR Sector Details

​Mixed Mode Encoding

​Subheader Information

​Data Sector Detection

​Creating STR Files

​From Video Sources

​From PlayStation SDK

​Extracting from Games

​Common STR Patterns

​Opening Cinematic

​Level Transitions

​Multiple Endings

​Audio in STR Files

​Synchronized Audio

​Audio Parameters

​Silent Video

​Video Parameters

​Resolution

​Frame Rate

​Color Depth

​EDC and ECC Handling

​Form 1 Sectors (Video)

​Form 2 Sectors (Audio)

​Troubleshooting

​Video Playback Issues

​Audio Desynchronization

​Stuttering or Dropped Frames

​Incorrect Sector Detection

​Performance Optimization

​Bitrate Considerations

​File Size Management

​Strategic Placement

​Best Practices

​Quality Guidelines

​File Organization

​Compression Balance

​Next Steps

Build docs developers (and LLMs) love

What is STR Video?

STR File Structure

Adding STR Video to Your ISO

STR Sector Details

Mixed Mode Encoding

Subheader Information

Data Sector Detection

Creating STR Files

From Video Sources

From PlayStation SDK

Extracting from Games

Common STR Patterns

Opening Cinematic

Level Transitions

Multiple Endings

Audio in STR Files

Synchronized Audio

Audio Parameters

Silent Video

Video Parameters

Resolution

Frame Rate

Color Depth

EDC and ECC Handling

Form 1 Sectors (Video)

Form 2 Sectors (Audio)

Troubleshooting

Video Playback Issues

Audio Desynchronization

Stuttering or Dropped Frames

Incorrect Sector Detection

Performance Optimization

Bitrate Considerations

File Size Management

Strategic Placement

Best Practices

Quality Guidelines

File Organization

Compression Balance

Next Steps