[MPlayer-dev-eng] playing little endian format uncompressed PCM audio stream via RTSP

Ratin ratin3 at gmail.com
Thu Mar 20 01:02:58 CET 2008


When you stream audio over live555's component on mplayer, what decides the
audio data to be big endian vs little endian? I am specifying the format as
97 (dynamic format) with rtpmap being : 96 L16/8000 for single channel, 16
bit/sample, 8 khz sample rate audio. But mplayer somehow thinks audio data
is in  big endian format and attaches a BE -> LE conversion filter:

after getting "describe":

Initiated "audio/L16" RTP subsession on port 4770
....
...

after getting "play" command:


Building audio filter chain for 8000Hz/1ch/s16be -> 0Hz/0ch/??...
[libaf] Adding filter dummy
[dummy] Was reinitialized: 8000Hz/1ch/s16be
[dummy] Was reinitialized: 8000Hz/1ch/s16be
ao_dsound: Output Devices:
0 Primary Sound Driver <--
1 SoundMAX Digital Audio
2 Bluetooth Audio
ao_dsound: DirectSound initialized
ao_dsound: format s16be not supported defaulting to Signed 16-bit
Little-Endian
ao_dsound: Samplerate:8000Hz Channels:1 Format:s16le
ao_dsound: Buffersize:16000 bytes (1000 msec)
ao_dsound: primary buffer created
ao_dsound: secondary (stream)buffer created
AO: [dsound] 8000Hz 1ch s16le (2 bytes per sample)
AO: Description: Windows DirectSound audio output
AO: Author: Gabor Szecsi <deje at miki.hu>
Building audio filter chain for 8000Hz/1ch/s16be -> 8000Hz/1ch/s16le...
[dummy] Was reinitialized: 8000Hz/1ch/s16be
[libaf] Adding filter format
[format] Changing sample format from big-endian 16-bit signed int to
little-endian 16-bit signed int
[format] Accelerated endianness conversion only
[dummy] Was reinitialized: 8000Hz/1ch/s16be
[format] Changing sample format from big-endian 16-bit signed int to
little-endian 16-bit signed int
[format] Accelerated endianness conversion only
Video: no video
Freeing 0 unused video chunks.
Starting playback...
[libaf] Reallocating memory in module format, old len = 0, new len = 16000
No bind found for key ''.
A:  -1.0 (unknown) of 0.0 (unknown)  0.0%

I hear nothing but noise. The data is in little endian format.



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