# Network Abstraction Layer (NAL) adaptation flag reference
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This section contains information about available flags for the `StreamInfo.NalAdaptationFlags` enumeration.

The [elementary stream](https://en.wikipedia.org/wiki/Elementary_stream) in an application can be in either **Annex-B** or **AVCC** format: 
+ The **Annex-B** format delimits [NALUs (Network Abstraction Layer units)](https://en.wikipedia.org/wiki/Network_Abstraction_Layer#NAL_units) with two bytes of zeroes, followed by one or three bytes of zeroes, followed by the number *1* (called a **start code**, for example, 00000001). 
+ The **AVCC** format also wraps NALUs, but each NALU is preceded by a value that indicates the size of the NALU (usually four bytes).

Many encoders produce the Annex-B bitstream format. Some higher-level bitstream processors (such as a playback engine or the [Media Source Extensions (MSE)](https://en.wikipedia.org/wiki/Media_Source_Extensions) player in the AWS Management Console) use the AVCC format for their frames.

The codec private data (CPD), which is SPS/PPS (Sequence Parameter Set/Picture Parameter Set) for the H.264 codec, can also be in Annex-B or AVCC format. However, for the CPD, the formats are different from those described previously.

The flags tell the SDK to adapt the NALUs to AVCC or Annex-B for frame data and CPD as follows: 


****  

| Flag | Adaptation | 
| --- | --- | 
| NAL\$1ADAPTATION\$1FLAG\$1NONE | No adaptation. | 
| NAL\$1ADAPTATION\$1ANNEXB\$1NALS | Adapt Annex-B NALUs to AVCC NALUs. | 
| NAL\$1ADAPTATION\$1AVCC\$1NALS | Adapt AVCC NALUs to Annex-B NALUs. | 
| NAL\$1ADAPTATION\$1ANNEXB\$1CPD\$1NALS | Adapt Annex-B NALUs for the codec private data to AVCC format NALUs. | 
| NAL\$1ADAPTATION\$1ANNEXB\$1CPD\$1AND\$1FRAME\$1NALS | Adapt Annex-B NALUs for the codec and frame private data to AVCC format NALUs. | 

For more information about NALU types, see **Section 1.3: Network Abstraction Layer Unit Types** in [RFC 3984](https://www.ietf.org/rfc/rfc3984.txt).