Hi all, I'm a Slackware since a long time ago, currently running version 14.2 64bit (it is the first time I go 64) and I am having strange issues when playing videos.
In both Firefox and Chromium, when playing youtube videos (just to name a site, it happens with any site), I must move the cursor in the video window otherwise it stutters, loops or pauses, and during these episodes audio is sometimes in sync, sometimes goes back and forth not in sync.
Xine and Kplayer seem to be unaffected, unlikely due to some tweaks I've done in their configuration.
To solve a similar issue with audio I have disabled pulse where possible, but this is something I had to do also with some previous Slackware versions, too; again, I think it is unrelated.
The system is up-to-date by the time of writing; for what I rememeber, the issue has been there since the installation of Slackware 14.2, so problems don't come from patches.

Any clue? Heeeelp!!!
Information follow...

(uname -a)

Linux pharlap 4.4.88 #2 SMP Thu Sep 14 14:21:06 CDT 2017 x86_64 AMD Athlon(tm) II X3 450 Processor AuthenticAMD GNU/Linux

(lspci)

00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] RS780 Host Bridge
00:02.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780 PCI to PCI bridge (ext gfx port 0)
00:04.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 0)
00:0a.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 5)
00:11.0 SATA controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode]
00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:12.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller
00:12.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:13.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:13.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller
00:13.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 SMBus Controller (rev 3a)
00:14.1 IDE interface: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 IDE Controller
00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA)
00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 LPC host controller
00:14.4 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 PCI to PCI Bridge
00:14.5 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI2 Controller
00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor HyperTransport Configuration
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Address Map
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Miscellaneous Control
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 10h Processor Link Control
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV710 [Radeon HD 4350/4550]
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] RV710/730 HDMI Audio [Radeon HD 4000 series]
02:00.0 USB controller: Renesas Technology Corp. uPD720202 USB 3.0 Host Controller (rev 02)
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 02)
04:0e.0 FireWire (IEEE 1394): Texas Instruments TSB43AB23 IEEE-1394a-2000 Controller (PHY/Link)

Mozilla and Chromium versions (most likely, nothing to do with the issue):

mozilla-firefox-52.3.0esr-x86_64-1_slack14.2
chromium-61.0.3163.100-x86_64-1alien

a few packages that may have something to do with the issue:

alsa-lib-1.1.1-x86_64-2
alsa-oss-1.0.28-x86_64-1
alsa-plugins-1.1.1-x86_64-1
alsa-utils-1.1.1-x86_64-1
alsa-oss-1.0.28-x86_64-1
v4l-utils-1.10.0-x86_64-1
xf86-video-v4l-0.2.0-x86_64-13

(part of /etc/pulse/client.conf, with some changes)

# Ubi: was yes, but I am trying to solve some sound issues:
autospawn = no
# Ubi: was yes:
allow-autospawn-for-root = no

(some non-standard packages, I don't see any trouble here)

ORBit2-2.14.19-x86_64-3_SBo
SDL2-2.0.5-x86_64-1_SBo
SDL2_image-2.0.1-x86_64-2_SBo
SDL2_mixer-2.0.1-x86_64-2_SBo
SDL2_net-2.0.1-x86_64-1_SBo
SDL2_ttf-2.0.14-x86_64-1_SBo
SDL_Pango-0.1.2-x86_64-3_SBo
SDL_gfx-2.0.25-x86_64-1_SBo
imlib2-1.4.10-x86_64-1_SBo
leptonica-1.74.4-x86_64-1_SBo
libdvdcss-1.4.0-x86_64-2_SBo

(/etc/asound.conf, pulse skipped)

# Ubi: commented these two lines:
#pcm.default pulse
#ctl.default pulse

is your browser using the flash player to play the content or html5?

if it's the flash player, some settings are tweakable: https://wiki.archlinux.org/index.php...#Configuration

None of the browsers is using Flash when the issue occurs.
What happens is that after a few seconds, rarely a bit more, the video freezes and the audio loops a couple of seconds of the track.
In Firefox, if I ritgh-click on "Stats for nerds" while the video is running, I see the two bars but they freeze with the rest of the video.
I'd rule out the video kernel modules, such as the DRM module, but can I be sure?
I also add this information (ecluded modules that really really cannot have anythig to do with it like tpm, ipv6, fuse, kvm*, serio_raw...):

snd_hda_codec_hdmi 39395 1
i2c_dev 6252 0
ppdev 6286 0
snd_hda_codec_realtek 73238 1
snd_hda_codec_generic 61189 1 snd_hda_codec_realtek
psmouse 112828 0
evdev 13220 16
k10temp 3832 0
amdkfd 72324 1
amd_iommu_v2 8390 1 amdkfd
radeon 1484367 2
hwmon 4199 2 k10temp,radeon
ttm 82385 1 radeon
drm_kms_helper 119004 1 radeon
snd_hda_intel 29531 5
snd_hda_codec 108205 4 snd_hda_codec_realtek,snd_hda_codec_hdmi,snd_hda_codec_generic,snd_hda_intel
i2c_piix4 9447 0
drm 323286 5 ttm,drm_kms_helper,radeon
snd_hda_core 52370 5 snd_hda_codec_realtek,snd_hda_codec_hdmi,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel
snd_hwdep 6656 1 snd_hda_codec
agpgart 31796 2 drm,ttm
snd_pcm 92738 4 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel,snd_hda_core
i2c_algo_bit 5962 1 radeon
fb_sys_fops 1730 1 drm_kms_helper
syscopyarea 3458 1 drm_kms_helper
snd_timer 22109 1 snd_pcm
sysfillrect 3950 1 drm_kms_helper
sysimgblt 2608 1 drm_kms_helper
i2c_core 47925 6 drm,i2c_dev,i2c_piix4,drm_kms_helper,i2c_algo_bit,radeon
snd 69051 17 snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel
r8169 73063 0
soundcore 6876 1 snd
xhci_pci 5065 0
xhci_hcd 117433 1 xhci_pci
wmi 9259 0
mii 5143 1 r8169
fjes 21479 0
ohci_hcd 29364 1 ohci_pci
ehci_pci 4285 0
ehci_hcd 44114 1 ehci_pci
shpchp 26296 0
acpi_cpufreq 8189 0
8250_fintek 3214 0
processor 28718 1 acpi_cpufreq
button 5943 0
loop 21334 0

Could your problem perhaps be something external like your Internet connection or your router and not necessarily your PC or the Slackware install itself? Does streaming video work OK on any other devices you also have connected to your LAN? What kind of bandwidth speed do you typically get from your cable/DSL connection?
... and this is a remote possibility but check the Ethernet cable feeding your PC.

Definitely not a network issue. Apart from that every other PC at home does fine, the Chromium "Nerd Stats" shows the buffer is OK.
The point is: if I move the mouse in the video frame or Chromium (or Firefox) window, everything is OK, this is crazy! Seems like that activity on the window is related with its "priority" (what would the mouse interaction have to do with it, otherwise?) and that as soon the priority drops video playing goes nuts.
If I stop moving the mouse, after a few seconds, sometimes a minute, the video stops paying and audio loops (an excerpt of seconds).
If I move the mouse in the window, it is perfectly working. Tried many many times.

I've just verified that any activity will keep the video alive, also just pressing keys on the keyboard in another program window.

I can't say for certain on an AMD/ATi system as I always get nVidia but when a function freezes unless you interrupt the system with mouse or keyboard activity usually indicates a driver problem and likely the graphics system driver at that.

I've fully solved the issue by installing a new card (GT 730).
Unlikely the AMD card was driver, probably it was the driver. Sigh.

What quality of video were you trying? I spent a bit of time this last weekend, solving the same very thing. You said earlier that it is likely not the web browser, but then mentioned that Xine, Kplayer was fine. Then this means it isn't the driver/card, but the browser.

I installed a ATI HD6450 in an old single core Athlon 64. This replaced an RS480 (Xpress 200M) ATI, which really doesn't have much HW support in video decoding in Linux. This gave an instant improvement in MPlayer (vdpau active now), but not with Seamonkey. Note your RV710 should have vdpau support, so that explains your original report.

So looking into this discrepancy, I found that recent versions of Seamonkey/Firefox (Mozilla browsers) lack completely any HW support for graphics. This proves the browser is the issue. I found Chromium on Linux generally blacklists the HW support on Linux, except it can be forced on in chrome://gpu. For Chromium HW video decoding, it's not supported at this time in Linux, but there is work being done, and it can be compiled and tested. I enabled the HW support in Chromium, and it noticeably improved performance. And that you have an Athlon X3, you should get pretty decent improvement for the multi-threading I see Chromium uses.

For an alternative to all this, you can try the flash option, which the plugin is supposed to support HW video decoding on Linux, but I don't use flash at all, so I don't know if it supports ATI.

On beefy systems, if no one noticed, they are likely have really good CPU / BUS, that likely makes up the difference with the lack of video HW support in browsers in Linux. I know for that, I never noticed this issue on my main system. Here I use ATI HD4670 on a quad core, and never noticed the lack of proper support.

Actually, before buying the new card I have spent some more time testing, and I had issues also with stand-alone players.
For instance, one player (I think it was KPlayer, but I can't test any more) sometimes displayed a black window instead of the video (but sound was there). Same file opened immediately after, same player... and I got the video!
Behaviour was too irregular to spot a certain cause, I gave up and tried with a new card.
Also... videos in browsers should work without hardware acceleration, too, right?!

There is a possibility that there was a bug in the driver or player, causing a crash, or a bad use of resources, that required opening the video a second time. But this is speculative without looking into it. There could be a system or software config issue as well. But I think it's probably ok you ditched the card. It's one of the slowest cards. I'm not sure how much vdpau could squeeze out of it, without more info, but it's not worth it.

On your question on video in browsers. Yes you can run without HW accel, but you need a beefy CPU to compensate. It's hard to understand how I've gone so long without noticing this myself in the browser. But html5 video coming in more use, now I realize how bad certain browsers are at supporting a decent playback as I set up more machines in Linux. I used to play everything through mplayer, so I never needed to deal with how bad flash was.