Leading silence (gaps) in audio segments

[litchfield]

I'm seeing gaps (silence) at the beginning of each audio segment.

Segment 1 = no gap,
Segment 2 = 1s gap,
Segment 3 = 2s gap,
Segment 4 = 3s gap,
... and so on.

This causes gaps/pops/clicks in playback.

Both mediastreamsegmenter and mediafilesegmenter are all fine (no gaps) on same source file (libfaac mpegts via ffmpeg).

All tests are using same default segment duration 10s.

[litchfield]

FFmpeg version 0.6.2

[ghost]

Can you post a small sample from the input file you are using? Or does it happen on all files?

[litchfield]

Here's the command I use to process them --

    ffmpeg -y -i "%(source)s" -acodec libfaac -vn -ab 64k -ac 1 -f mpegts - | \
    m3u8-segmenter -i - -d 10 -p fanchants-free -m fanchants-free.m3u8 -u %(target_urldir)s \

[ghost]

Thanks I'll take a look at these

[ghost]

Hmm. Interestingly enough the m3u8 loop plays fine under mplayer for me, but when I stream it to the iPhone I do get the popping and clicking.

[litchfield]

Weird huh, now try opening the ts files in an editor (eg Audacity) and you'll see the gaps

[ghost]

Out of interest, does the same problem occur if you retain both channels (-ac 2) when converting to aac ?

[litchfield]

Yep, same problem -ac 1 vs -ac 2.

Also tried --

• Both libfaac and aac (ffmpeg experimental version)
• Various segment lengths, same problem
• Various bit rates
• From file instead of from stdin

[ghost]

My command line is this (ffmpeg 0.8.5.git-751a4e):

ffmpeg -i http://stream-tx1.radioparadise.com:9000/rp_192.ogg -f mpegts -acodec libfaac -ab 128000 -| ../m3u8-segmenter/m3u8-segmenter -i - -d 1 -p media -m index.m3u8 -u http://localhost/aac/ -n 60

In addition to the pops and clicks, the program segfaults after starting the 49th file:

  Abort trap: 6kB time=00:00:48.83 bitrate= 143.4kbits/s 

I'm looking into the problem, but I'm just a first year :)

[D0023R]

Hi,

The gaps might be introduced with the header added to each segment. The following patch fix it:

--- m3u8-segmenter.c_ori 2011-11-23 10:39:17.000000000 +0100
+++ m3u8-segmenter.c 2011-11-23 10:39:41.000000000 +0100
@@ -469,11 +469,13 @@
break;
}

+if(0) {
// Write a new header at the start of each file
if (avformat_write_header(oc, NULL)) {
fprintf(stderr, "Could not write mpegts header to first output file\n");
exit(1);
}
+}

         prev_segment_time = segment_time;
     }

Rgds

Alex

[ghost]

That works! Thanks a bunch!

[litchfield]

Bradskins- we ended up taking your tip and using httpsegmenter instead- thanks- it still seems to include the silence but the pops/clicks were gone.

Will check out this patch at some point as we'd prefer no gaps at all (even if u can't hear em)

[ghost]

After applying the patch I ended up using both :). httpsegmenter is good
for streaming and m3u8-segmenter is good for encoding static files. One
thing I've noticed none of them do well: support for relative paths instead
of full URLs. It's entirely possible to use ./media-1.ts, ./media-2.ts in
your m3u8 file instead of putting the whole URL. I'll probably mention
something to both projects soon.

Regards,

-brad

On Mon, Nov 28, 2011 at 9:14 PM, s29 <
reply@reply.github.com

wrote:

Bradskins- we ended up taking your tip and using httpsegmenter instead-
thanks- it still seems to include the silence but the pops/clicks were gone.

Will check out this patch at some point as we'd prefer no gaps at all
(even if u can't hear em)

---

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