[osflash] flv file format question
nikos.k at arcww.gr
Wed Nov 18 01:13:56 PST 2009
An alternative strategy could be to use ffmpeg to transcode flv into mp3.
The real challenge is to find a recent compiled executable that support the
Nellymoser/ Speex (assuming that the source is the user mic).
From: osflash-bounces at osflash.org [mailto:osflash-bounces at osflash.org] On
Behalf Of Jeff Ramin
Sent: Wednesday, November 18, 2009 12:37 AM
To: Open Source Flash Mailing List
Subject: [osflash] flv file format question
I want to read an FLV file for the purpose of transcoding the audio,
and I'm using classes from the red5 project to iterate through the
tags in the file.
The section of the http://osflash.org/flv page on audio states:
FLV Tag 0x08: AUDIO
The first byte of an audio packet contains bitflags that describe the codec
used, with the following layout:
(byte & 0×01) » 0
0: mono, 1: stereo
(byte & 0×02) » 1
0: 8-bit, 1: 16-bit
(byte & 0x0C) » 2
0: 5.5 kHz, 1: 11 kHz, 2: 22 kHz, 3: 44 kHz
(byte & 0xf0) » 4
0: Uncompressed, 1: ADPCM, 2: MP3, 5: Nellymoser 8kHz mono, 6: Nellymoser,
The rest of the audio packet is simply the relevant data for that format, as
per a SWF <http://osflash.org/swf> SoundStreamBlock.
However, when I dump the first few bytes of audio data from consecutive
I see this pattern:
tag 1: b2 2a d7 5b
tag 2: b2 2a d7 5a
tag 3: b2 2a d7 5a
tag 4: b2 2a d7 5a
It seems there is more header data than a single byte. Is anybody familiar
with FLV file formats and audio data (speex encoded, in this instance) that
could clear this up for me?
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