V4L/DVB (4193): Update cx2341x fw encoding API doc.

Based on recent tests it turned out that some features are not implemented.
This has now been documented.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 18 insertions, 2 deletions

diff --git a/Documentation/video4linux/cx2341x/fw-encoder-api.txt b/Documentation/video4linux/cx2341x/fw-encoder-api.txt
index 08ee9f5303f9..f74b0ae4a769 100644
--- a/Documentation/video4linux/cx2341x/fw-encoder-api.txt
+++ b/Documentation/video4linux/cx2341x/fw-encoder-api.txt
@@ -100,13 +100,20 @@ Param[1]
 Name    CX2341X_ENC_SET_BIT_RATE
 Enum    149/0x95
 Description
-        Assign average video stream bitrate.
+        Assign average video stream bitrate. Note on the last three params:
+        Param[3] and [4] seem to be always 0, param [5] doesn't seem to be used.
 Param[0]
         0=variable bitrate, 1=constant bitrate
 Param[1]
         bitrate in bits per second
 Param[2]
         peak bitrate in bits per second, divided by 400
+Param[3]
+        Mux bitrate in bits per second, divided by 400. May be 0 (default).
+Param[4]
+        Rate Control VBR Padding
+Param[5]
+        VBV Buffer used by encoder
 
 -------------------------------------------------------------------------------
 
@@ -115,10 +122,11 @@ Enum 	151/0x97
 Description
         Setup the GOP structure
 Param[0]
-        GOP size
+        GOP size (maximum is 34)
 Param[1]
         Number of B frames between the I and P frame, plus 1.
         For example: IBBPBBPBBPBB --> GOP size: 12, number of B frames: 2+1 = 3
+        Note that GOP size must be a multiple of (B-frames + 1).
 
 -------------------------------------------------------------------------------
 
@@ -241,6 +249,9 @@ Name 	CX2341X_ENC_SET_STREAM_TYPE
 Enum    185/0xB9
 Description
         Assign stream type
+        Note: Transport stream is not working in recent firmwares.
+        And in older firmwares the timestamps in the TS seem to be
+        unreliable.
 Param[0]
          0=Program stream
          1=Transport stream
@@ -278,6 +289,8 @@ Description
                 '01' Layer III
                 '00' Undefined
         This discrepancy may indicate a possible error in the documentation.
+        Testing indicated that only Layer II is actually working, and that
+        the minimum bitrate should be 192 kbps.
 Param[0]
         Bitmask:
            0:1  '00' 44.1Khz
@@ -313,6 +326,9 @@ Param[0]
                 '01'=JointStereo
                 '10'=Dual
                 '11'=Mono
+                Note: testing seems to indicate that Mono and possibly
+                JointStereo are not working (default to stereo).
+                Dual does work, though.
 
           10:11 Mode Extension used in joint_stereo mode.
                 In Layer I and II they indicate which subbands are in