I had some problems in viewing recordings and now I set up inside /etc/mythtv/modules/ivtv the line
options ivtv yuv_buffers=8 mpg_buffers=32 vbi_buffers=8 pcm_buffers=8

The problem is that I cannot see something like
Allocate DMA encoder MPEG stream: 1024 x 32768 buffers (32768KB total)
inside the kern.log file....How I know that really the buffers are like in config?

For the version of the ivtv driver provide with R5F27 those option names now start with "enc_" for example: mpg_buffers -> enc_mpg_buffers

sorry..my mistake...I'm using R5E50...so I think is correct the settings...
but I don't know how to look in really ivtv is using my new buffer settings..

Here is what I have....I cannot realize if my changes had effect or not...

Oct 28 18:10:06 mythtv kernel: ivtv: ==================== START INIT IVTV ====================
Oct 28 18:10:06 mythtv kernel: ivtv: version 0.8.2 (tagged release) loading
Oct 28 18:10:06 mythtv kernel: ivtv: Linux version: 2.6.18-chw-13 SMP preempt mod_unload 586 gcc-4.1
Oct 28 18:10:06 mythtv kernel: ivtv: In case of problems please include the debug info between
Oct 28 18:10:06 mythtv kernel: ivtv: the START INIT IVTV and END INIT IVTV lines, along with
Oct 28 18:10:06 mythtv kernel: ivtv: any module options, when mailing the ivtv-users mailinglist.
Oct 28 18:10:06 mythtv kernel: ivtv0: Autodetected Hauppauge card (cx23415 based)
Oct 28 18:10:06 mythtv kernel: ACPI: PCI Interrupt Link [APC2] enabled at IRQ 17
Oct 28 18:10:06 mythtv kernel: ACPI: PCI Interrupt 0000:01:07.0[A] -> Link [APC2] -> GSI 17 (level, low) -> IRQ 20
Oct 28 18:10:06 mythtv kernel: ivtv0: loaded v4l-cx2341x-enc.fw firmware (262144 bytes)
Oct 28 18:10:06 mythtv kernel: ivtv0: loaded v4l-cx2341x-dec.fw firmware (262144 bytes)
Oct 28 18:10:06 mythtv kernel: tuner 2-0043: chip found @ 0x86 (ivtv i2c driver #0)
Oct 28 18:10:06 mythtv kernel: tda9887 2-0043: tda988[5/6/7] found @ 0x43 (tuner)
Oct 28 18:10:06 mythtv kernel: tuner 2-0061: chip found @ 0xc2 (ivtv i2c driver #0)
Oct 28 18:10:06 mythtv kernel: msp3400 2-0040: MSP4418G-B3 found @ 0x80 (ivtv i2c driver #0)
Oct 28 18:10:06 mythtv kernel: msp3400 2-0040: MSP4418G-B3 supports nicam and radio, mode is autodetect and autoselect
Oct 28 18:10:06 mythtv kernel: saa7115 2-0021: saa7115 found @ 0x42 (ivtv i2c driver #0)
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: Hauppauge model 48139, rev K2B7, serial# 9927438
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: tuner model is Philips FM1216ME MK5 (idx 117, type 4)
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: TV standards PAL(B/G) PAL(I) SECAM(L/L') PAL(D/D1/K) (eeprom 0x74)
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: audio processor is MSP4418 (idx 25)
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: decoder processor is SAA7115 (idx 19)
Oct 28 18:10:06 mythtv kernel: tveeprom 2-0050: has radio, has IR remote
Oct 28 18:10:06 mythtv kernel: ivtv0: Autodetected Hauppauge WinTV PVR-350
Oct 28 18:10:06 mythtv kernel: ivtv0: tveeprom cannot autodetect tuner!<6>saa7127 2-0044: saa7129 found @ 0x88 (ivtv i2c driver #0)
Oct 28 18:10:06 mythtv kernel: ivtv0: Encoder revision: 0x02050032
Oct 28 18:10:06 mythtv kernel: ivtv0: Decoder revision: 0x02020023
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device video0 for encoder MPEG
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device video32 for encoder YUV
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device vbi0 for encoder VBI
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device video24 for encoder PCM audio
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device radio0 for encoder radio
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device video16 for decoder MPEG
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device vbi8 for decoder VBI
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device vbi16 for decoder VOUT
Oct 28 18:10:06 mythtv kernel: ivtv0: Registered device video48 for decoder YUV
Oct 28 18:10:06 mythtv kernel: ivtv0: loaded v4l-cx2341x-init.mpg firmware (155648 bytes)
Oct 28 18:10:06 mythtv kernel: tuner 2-0061: tuner type not set
Oct 28 18:10:06 mythtv kernel: tuner 2-0061: tuner type not set
Oct 28 18:10:06 mythtv kernel: ivtv0: Initialized Hauppauge WinTV PVR-350, card #0
Oct 28 18:10:06 mythtv kernel: ivtv: ==================== END INIT IVTV ====================

There's your problem... And here...

You have the MK5 version of the card. This is covered in multiple places in the troubleshooting pages on the wiki:
http://www.knoppmythwiki.org/index.php?page=BlackScreenWatchingTV
http://www.knoppmythwiki.org/index.php?page=CheckingLogFiles
Both of which point you to...
http://www.knoppmythwiki.org/index.php?page=TVCaptureCards