Chibi Jasmin
13th June 2002, 08:58
I used Nandub to mux a video with AC3-Sound.
One time I directly used AC3, other time I chose AC3 with WAV-Header. Resulting files had same size, both played fine. But a fc /b compare (byte by byte) showed them to be entirely different...
Can someone explain what the difference is and why? Is there any drawback in adding a wav-header to ac3 and then muxing it?
UPDATE: Well, after some experimenting, I found out that both ways produce exactly the same output AFTER Inter Video Audio Decoder in the filter chain (I dumped the output into a file with dump filter and compared). So there seems to be no difference in output at least. At every point before Inter Video Audio decoder in the filter chain the dumped output was different...wav header seems to be taken over into the final avi and then through the whole direct show chain until it gets stripped by Inter Video Audio Decoder...
BTW: The dumped video output was the same in both files, too.
Leaving the question (as both files had sime size), where the wav-header is stored in the muxed file...maybe somewhere, where the file without header just has unused data? Or maybe it isn't the wav-header that makes different files / dump output before Audio Decoder? As the output of both versions (Muxing AC3 or AC3-WAV) are identical it is not really important, but I'd still be interested to get information, what makes the difference in both possibilities.
One time I directly used AC3, other time I chose AC3 with WAV-Header. Resulting files had same size, both played fine. But a fc /b compare (byte by byte) showed them to be entirely different...
Can someone explain what the difference is and why? Is there any drawback in adding a wav-header to ac3 and then muxing it?
UPDATE: Well, after some experimenting, I found out that both ways produce exactly the same output AFTER Inter Video Audio Decoder in the filter chain (I dumped the output into a file with dump filter and compared). So there seems to be no difference in output at least. At every point before Inter Video Audio decoder in the filter chain the dumped output was different...wav header seems to be taken over into the final avi and then through the whole direct show chain until it gets stripped by Inter Video Audio Decoder...
BTW: The dumped video output was the same in both files, too.
Leaving the question (as both files had sime size), where the wav-header is stored in the muxed file...maybe somewhere, where the file without header just has unused data? Or maybe it isn't the wav-header that makes different files / dump output before Audio Decoder? As the output of both versions (Muxing AC3 or AC3-WAV) are identical it is not really important, but I'd still be interested to get information, what makes the difference in both possibilities.