Current status of Stagefright

• Local file playback (AMR/MP3/MP4/...) and basic http playback support;
• Video only recording;
• A corresponding metadata retriever, not fully implemented yet.

Some thoughts on the enhancement:

• No abstraction layer for media sink, and lack of a pluggable mechanism to pick decoder dynamically based on the source's format and sink's capability. The overall architecture doesn't seem to be flexible enough to date;
• It's good to re-use the same MediaExtractor from player engine for metadata retrieving to avoid duplication. However, MediaExtractor itself might not get all required keys reliably, e.g. it might be more accurate to get some keys (e.g, video height/width) from decoder's output;
• To support audio only and audio+video recording;
• Http support is not complete, no BUFFERING status update, not asynchronous message for data insufficient/available;
• No RTSP support yet.

Anyway, it's still under active development and it's from Google, so it wouldn't be surprising that it evolves quickly as a replacement of OpenCORE in the near future;)

An overview of Stagefright player

There is a new playback engine implemented by Google comes with Android 2.0 (i.e, Stagefright), which seems to be quite simple and straightforward compared with the OpenCORE solution.

• MediaExtractor is responsible for retrieving track data and the corresponding meta data from the underlying file system or http stream;
• Leveraging OMX for decoding: there are two OMX plugins currently, adapting to PV's software codec and vendor's hardware implementation respectively. And there is a local implementation of software codecs which encapsulates PV's decoder APIs directly;
• AudioPlayer is responsible for rendering audio, it also provides the timebase for timing and A/V synchronization whenever audio track is present;
• Depending on which codec is picked, a local or remote render will be created for video rendering; and system clock is used as the timebase for video only playback;
• AwesomePlayer works as the engine to coordinate the above modules, and is finally connected into android media framework through the adapter of StagefrightPlayer.

Static diagram of OpenCORE Player Engine

Fix syntax highlighter in the blogger template

Sep-17th - It seems syntax highlighter has updated, so my code snippet is in a mess again:(

Sep-30th:

Revert to R92. Change the template as following:

<link href='http://flash-host.com.br/blog/sh/SyntaxHighlighter.css' rel='stylesheet' type='text/css'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shCore.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushCSharp.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushXml.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushPython.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushJScript.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushCpp.js'/> 
<script language='javascript' src='http://syntaxhighlighter.googlecode.com/svn-history/r92/trunk/Scripts/shBrushBash.js'/> 
<script language='javascript'> 
 
  dp.SyntaxHighlighter.BloggerMode();
  dp.SyntaxHighlighter.HighlightAll('code');
 
</script>

Opencore logs and releases

1. Enable Opencore 2.0x logs:
1)At compilation time, add the marco ENABLE_PV_LOGGING=1
$ cd <android_home>
$ touch external/opencore/oscl/oscl/osclbase/src/pvlogger.h
$ make ENABLE_PV_LOGGING=1
2)At runtime, /sdcard/pvlogger.txt is used to specify enabled log level and related tags. (write 8 alone in it will enable all pv logs.) Below is extracted from external/opencore/android/android_logger_config.h:
/*
To configure logging at runtime, a file pvlogger.txt must be located in the sdcard.
The format for log level and logger tag in the file should be: "level,node". Note that there should be no space between log level and logger tag.
For example, pvlogger.txt can look like:
1,PVPlayerEngine
8,PVSocketNode
Above example means log the message level PVLOGMSG_ALERT for PVPlayerEngine and PVLOGMSG_DEBUG for PVSocketNode. See pvlogger.h for log level values.
*/

2. Enable Opencore 1.0 logs:
1)Change external/opencore/oscl/pvlogger/src/pvlogger.h:
/* Release mode-- No logging */
#define PVLOGGER_INST_LEVEL 0 ---- Change this value to 5
2)Change external/opencore/android/thread_init.cpp:
#if 0 --------- Change this value to 1
PVLoggerAppender *appender = new
AndroidLogAppender();
...
...
#endif
3)Rebuild android source.

PV Releases:
PV2.04: http://groups.google.com/group/android-framework/browse_thread/thread/ccec12e4fe876149/17254e4a88875a6b
PV2.02: http://groups.google.com/group/android-framework/browse_thread/thread/8b72bdad6ca508e/33033406a6b2e0d0
PV2.01: http://groups.google.com/group/android-framework/browse_thread/thread/5712f642dbee9398/f943ebc7ec02bb18
PV2.0: http://groups.google.com/group/android-framework/browse_thread/thread/92e10684c6f09e16/8df445f867c19f2e

World Reading Day

Below is a list of good software books:
Top 100 Best Software Engineering Books, Ever

Personally, I am a little surprised that Eric Evans' "Domain-Driven Design" ranks so low. And "Object Design: Roles Responsibilities and Collaborations" by Rebecca Wirfs-Brock is not on the list which is also worth reading:)

As someone commented, the list is more likely to be based on the popularity (good or not is really a subjective judgment which lacks the objective criteria:), but still, a good reference for reading.

(BTW: The original creator of the list has published another list of Top 50 New Software Development Books which may still need time proven:)

Tips for debugging mediaserver

1. Add symbol file for dynamically loaded so, e.g. libopencore_asflocal.so
(1) Find where the module was loaded:
#cat /proc/<pid>/maps
a7c26000-a7c52000 r-xp 00000000 1f:06 1060 /system/lib/libopencore_asfloca
l.so
a7c52000-a7c54000 rw-p 0002c000 1f:06 1060 /system/lib/libopencore_asfloca
l.so

(2) Get the text section's offset within the module:
$objdump --section-headers out/target/product/generic/symbols/system/lib/libopencore_asflocal.so |grep text
6 .text 0001679c 0000e3c8 0000e3c8 0000e3c8 2**3

(3) Add this offset to the load address of the module to obtain the relocation address for the module's code: (0xa7c26000+0x0000e3c8 = 0xa7c343c8)
(gdb)add-symbol-file out/target/product/generic/symbols/system/lib/libopencore_asflocal.so 0xa7c343c8

2. Switch between threads inside mediaserver process
(gdb) info threads
(gdb) thread <id>

[1]Debugging with GDB
[2]Debugging Loadable Modules Using GDB
[3]Debugging programs with multiple threads