Problem with blip in audio

[Eamon21]

I'm trying to convert a number of .MOV files to mp4 but I keep having audio problems in that the audio always seems to have a blip at the beginning and run longer than the video.

trying to uncover the cause I did the following which I would appreciate it if someone else could try with their own sources and see if the same thing happens:

I took various wave files (around 3 seconds to make it easy) and manually encode them with neroAACEnc. Using Nero Wave editor, the resulting mp4 file looked OK and very closely resembled input wav file and was the same length of 3 seconds exactly - however, MP4Box reported that the length of the audio track was in fact longer than the wave file, the difference varied according to source file but one example was 3.328 seconds.

Now if i use YAMB to extract the track and open that in the wave editor, the extracted AAC file has a blip at the beginning, then a bit of silence then the rest of the audio and runs for 3.328 seconds.

Also, if I take the output of the Nero encode and try to mux that in with the video, the sound now resembles what I get from the extracted AAC file, with the blip and extended length.

Is this a problem with MP4Box? It is driving me crazy!!!

Eamon

[burfadel]

Have you tried different versions of mp4box? there's a lot of builds floating around the place.

[Eamon21]

Yeah, I have tried the version that comes with current build of YAMB (doesn't show a version), also the 4.4 and 4.5 dev versions from official site, all say the audio track is 3.328 seconds in length.

[Eamon21]

I've uploaded the files I was using if anyone wants a look @ http://www.mytempdir.com/2061934

the three files are:
test.wav - the original Wave file
test_nero.mp4 - the output of the neroAACEnc
test_nero_track1.aac - the aac track extracted from test_nero.mp4 using YAMB

Also, here are scrrensots of the waveform of each file in Nero Wave editor. You can see in the third one the problem at the beginning of the track. Also just noticed that it seems to think the aac track is stereo when it is(should be) mono.

test.wav
http://img225.imageshack.us/img225/6916/testwavva4.th.png (http://img225.imageshack.us/my.php?image=testwavva4.png)

test_nero.mp4
http://img225.imageshack.us/img225/962/testneromp4yo5.th.png (http://img225.imageshack.us/my.php?image=testneromp4yo5.png)

test_nero_track1.aac
http://img221.imageshack.us/img221/7250/testnerotrack1aacfz1.th.png (http://img221.imageshack.us/my.php?image=testnerotrack1aacfz1.png)

[montython]

I replicate your results. This is what I get when I check the encoded mp4 file with the DSM Converter option of Media Player Classic:

http://i231.photobucket.com/albums/ee166/img_f/chptr.png

Notice the chapters part. The audio stream starts after a delay of 0.328 seconds. The same thing happens for anything encoded with Nero AAC Encoder (v1.1.34.2). Usually the delay is much shorter compared to this and we just don't notice it.

This has nothing to do with Yamb or mp4muxer. I cannot think of anything else except that this is a bug with Nero AAC Encoder. This doesn't happen with other encoders. I am sure there are other people who noticed this before...


I noticed one more thing: The blip is not audible when the mp4 file is played back with mplayer. After observing this, I thought maybe it could be a problem with the mp4 splitter. I tried both the Gabest mp4 splitter and the Haali media splitter. The blip is there in both cases.

I don't own the Nero bloatware and I have no intentions to install a trial version. It seems that you have it installed in your PC. Maybe you can test the Nero mp4 splitter and post the results...

[Eamon21]

Thanks montython, at least I know it's not just me. I had noticed that the length varies with the file encoded, sometime longer, sometimes shorter than .328 seconds. Problem is it never seems to be the same length as the input

I've done the same thing with FAAC encoder and in this instance it produces a file 3.128 seconds long so I don't think it is isolated to the Nero encoder.

gspot doesn't specify what splitter is being used and I'm not sure how to check that though I do have the halli media splitter installed.

I tried the same thing with mp3 and while the encoded mp3 showed the following in foobar:
Duration : 0:03.000 (24000 samples)
Sample Rate : 8000 Hz
Channels : 1
Bitrate : 44 kbps
Codec : MP3
Codec Profile : MP3 ABR
Encoding : lossy
Tool : LAME3.98a
<ENC_DELAY> : 576
<ENC_PADDING> : 1344
<MP3_ACCURATE_LENGTH> : yes
<MP3_STEREO_MODE> : mono

once it was muxed into the mp4, it showed:

Track # 2 Info - TrackID 2 - TimeScale 8000 - Duration 00:00:03.240
Media Info: Language "Undetermined" - Type "soun:mp4a" - 45 samples
MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x69
MPEG-2.5 Audio - 1 Channel(s) - SampleRate 8000 - Layer 3
Synchronized on stream 1

I am officially loosing it.

Eamon